Home Photographic Guide to Larval Reef Fishes Publications Curriculum vitae Projects Inventory Contact
  for pdf reprints, click on the title of the articles below
Victor, BC (2016) Journal of the Ocean Science Foundation
23: 21-50
Two new species in the spike-fin fairy-wrasse species complex (Teleostei: Labridae: Cirrhilabrus) from the Indian Ocean
Journal of the Ocean Science Foundation
22: 10-27
Victor, BC (2016)
Halichoeres gurrobyi, a new labrid fish (Teleostei: Labridae) from Mauritius in the southwestern Indian Ocean, with a review of the H. zeylonicus species complex
Victor, BC and Edward, JMB (2016) Journal of the Ocean Science Foundation
21: 58-70
Pseudojuloides labyrinthus, a new labrid fish (Teleostei: Labridae) from the western Indian Ocean
Journal of the Ocean Science Foundation
18: 1-77
Randall, JE and Victor, BC (2015)
Descriptions of thirty-four new species of the fish genus Pempheris (Perciformes: Pempheridae), with a key to the species of the western Indian Ocean
Victor, BC, Valdez-Moreno, M and Vásquez-Yeomans, L. (2015) DNA Barcodes
2015 (3): 85-93
Status of DNA Barcoding Coverage for the Tropical Western Atlantic Shorefishes and Reef Fishes
Journal of the Ocean Science Foundation
16: 1-55
Randall, JE, Connell, A.D. and Victor, BC (2015)
Review of the labrid fishes of the Indo-Pacific Genus Pseudocoris, with a description of two new species
Victor, BC and Edward, JMB (2015) Journal of the Ocean Science Foundation
15: 41-52
Pseudojuloides zeus, a new deep-reef wrasse (Perciformes: Labridae) from Micronesia in the western Pacific Ocean

Cambridge University Press, Cambridge, United Kingdom
chapter 8: 76-87

email for pdf copy

book on Amazon

Victor, BC (2015)

Chapter 8

How many coral reef fish species are there? Cryptic diversity and the new molecular taxonomy

In: Mora, C. (Ed.) Ecology of Fishes on Coral Reefs

Connell, AD, Victor, BC and Randall, JE (2015) Journal of the Ocean Science Foundation
14: 49-56
A new species of Pseudojuloides (Perciformes: Labridae) from the south-western Indian Ocean
Journal of the Ocean Science Foundation
12: 61-83
Randall, JE and Victor, BC (2014)
Four new fishes of the genus Pempheris (Perciformes: Pempheridae) from the western Indian Ocean
Randall, JE, Victor, BC, Alpermann, TJ, Bogorodsky, SV, Mal, AO, Satapoomin, U and Bineesh, KK (2014) Zootaxa
3887: 377–392
Rebuttal to Koeda et al. (2014) on the Red Sea fishes of the perciform genus Pempheris
Bulletin of Marine Science 90(1):533–549 Bernardi, G, Ramon, ML, Alva-Campbell, Y, McCosker, JE, Bucciarelli, G, Garske, LE, Victor, BC and Crane, NL (2014)
Darwin’s fishes: phylogeography of Galápagos Islands reef fishes
Victor, BC (2014) Journal of the Ocean Science Foundation
12: 25-60
Three new endemic cryptic species revealed by DNA barcoding of the gobies of the Cayman Islands (Teleostei: Gobiidae)
Journal of the
Ocean Science

11: 1-12
Victor, BC and Randall, JE (2014)
Pseudojuloides edwardi, n. sp. (Perciformes: Labridae): an example of evolution of male-display phenotype outpacing divergence in mitochondrial genotype
Randall, JE and Victor, BC (2013) Journal of the Ocean Science Foundation
8: 44-61
Bodianus atrolumbus (Valenciennes 1839), a valid species of labrid fish from the southwest Indian Ocean
Journal of the
Ocean Science

8: 30-43
Victor, BC (2013)
Scorpaena wellingtoni n. sp., a new scorpionfish from the Galápagos Islands (Scorpaeniformes: Scorpaenidae)
Victor, BC (2013) Journal of the Ocean Science Foundation
7: 44-73
The Caribbean Roughhead Triplefin (Enneanectes boehlkei): DNA barcoding reveals a complex of four West Indian sympatric cryptic species (Teleostei: Blennioidei: Tripterygiidae)
3669: 551–570
Victor, BC, Alfaro, ME and Sorenson, L (2013)
Rediscovery of Sagittalarva inornata n. gen., n. comb. (Gilbert, 1890) (Perciformes: Labridae), a long-lost deepwater fish from the eastern Pacific Ocean: a case study of a forensic approach to taxonomy using DNA barcoding
Victor, BC and Wellington, GM (2013) Journal of the Ocean Science Foundation
6: 19-32
Citharichthys darwini n. sp., a new endemic flatfish from the Galápagos Archipelago (Teleostei: Pleuronectiformes: Paralichthyidae)
Journal of the
Ocean Science

5: 1-19
Victor, BC (2012)
Hypoplectrus floridae n. sp. and Hypoplectrus ecosur n. sp., two new Barred Hamlets from the Gulf of Mexico (Pisces: Serranidae): more than 3% different in COI mtDNA sequence from the Caribbean Hypoplectrus species flock
Baldwin, CC, Castillo, CI, Weigt, LA and Victor, BC (2011) ZooKeys
79: 21-72
Seven new species within western Atlantic Starksia atlantica, S. lepicoelia, and S. sluiteri (Teleostei, Labrisomidae), with comments on congruence of DNA barcodes and species
Journal of the
Ocean Science

4: 1-29
Victor, BC (2010)
Emblemariopsis carib and Emblemariopsis arawak, two new chaenopsid blennies from the Caribbean Sea: DNA barcoding identifies males, females, and juveniles and distinguishes sympatric cryptic species
Victor, BC and Randall, JE (2010) Zoological Studies
49(6): 865-871
Gramma dejongi, a new basslet (Perciformes: Grammatidae) from Cuba, a sympatric sibling species of G. loreto
Journal of the
Ocean Science Foundation

3: 1-16
Victor, BC (2010)
The Redcheek Paradox: the mismatch between genetic and phenotypic divergence among deeply-divided mtDNA lineages in a coral-reef goby, with the description of two new cryptic species from the Caribbean Sea
Victor, BC, Vasquez-Yeomans, L, Valdez-Moreno, M, Wilk, L, Jones, DL, Lara, M, Caldow, C and Shivji, M (2010) Zootaxa
2346: 53-61
The larval, juvenile, and adult stages of the Caribbean goby, Coryphopterus kuna (Teleostei: Gobiidae): a reef fish with a pelagic larval duration longer than the post-settlement lifespan
2215: 24-36
Victor, BC, Hanner, R, Shivji, M, Hyde, J and Caldow, C (2009)
Identification of the larval and juvenile stages of the Cubera Snapper, Lutjanus cyanopterus, using DNA barcoding
Victor, BC (2008) Journal of the Ocean Science Foundation
1: 1-19
Redescription of Coryphopterus tortugae (Jordan) and a new allied species Coryphopterus bol (Perciformes: Gobiidae: Gobiinae) from the tropical western Atlantic Ocean
1526: 51-61
Victor, BC (2007)
Coryphopterus kuna, a new goby (Perciformes: Gobiidae: Gobiinae) from the western Caribbean, with the identification of the late larval stage and an estimate of the pelagic larval duration
Robertson, DR, Karg, F, Leao de Moura, R, Victor, BC and Bernardi, G (2006) Molecular Phylogenetics and Evolution
40: 795-807
Mechanisms of speciation and faunal enrichment in Atlantic parrotfishes
ASIH 2006
meeting abstracts
Victor, BC (2006)
The late-stage larvae of Caribbean gobies, eleotrids, and microdesmids: identification guide and patterns of size and age at settlement
Victor, BC, Wellington, GM, Robertson, DR and Ruttenberg, BI (2001) Bulletin of Marine Science
69(1): 279-288
The effect of the El Niño-Southern Oscillation event on the distribution of reef-associated labrid fishes in the eastern Pacific Ocean
Proceedings of the Royal Society of London, B.
268: 1931-1936
Riginos, C and Victor, BC (2001)
Larval spatial distributions and other early life history characteristics predict genetic differentiation in eastern Pacific blennioid fishes
Victor, BC, Wellington, GM and Caldow, C (2001) Revista Biologia Tropical
49(1): 101-110
A review of the razorfishes (Perciformes:Labridae) of the eastern Pacific Ocean
In: D. and P. Hoply,
J. Talemander, and
T. Done, eds.
Proc. of the 9th
Int. Coral Reef Symposium
Abstracts 2000: 10
Victor, BC, Wellington, GM and Robertson, DR (2000)
The effect of El Nino on the distribution of reef-associated labrid fishes in the eastern Pacific Ocean
Victor, BC and Wellington, GM (2000) Marine Ecology Progress Series
205: 241-248
Endemism and the pelagic larval duration of reef fishes in the eastern Pacific Ocean
Copeia 1992
4: 1053-1059
Wellington, GM (1992) (collaboration)
Xyrichtys victori, a new species of razorfish from the Galapagos Islands (Teleostei: Labridae)
Wellington, GM and Victor, BC (1992) Marine Biology
113: 491-498
Regional differences in the planktonic larval duration of reef fishes in the eastern Pacific Ocean
In: Sale, P, ed.
The ecology of fishes on coral reefs.
Orlando, Florida,
Academic Press

1991: 231-60
Victor, BC (1991)
Settlement strategies and biogeography of reef fishes
Wellington, GM and Victor, BC (1989) Marine Biology
101: 557-567
Planktonic larval duration of one hundred species of Pacific and Atlantic damselfishes (Pomacentridae)
69: 370-381
Robertson, DR, Green, DG and Victor, BC (1988)
Temporal coupling of production and recruitment of larvae of a Caribbean reef fish
Wellington, GM and Victor, BC (1987) American Naturalist
131: 588-601
Variation in components of reproductive success in an undersaturated population of a coral reef damselfish: a field perspective
Bulletin of Marine Science
40: 152-160
Victor, BC (1987)
The mating system of the Caribbean rosy razorfish, Xyrichtys martinicensis
Victor, BC (1987) Marine Biology
95: 145-152
Growth, dispersal, and identification of planktonic labrid and pomacentrid reef-fish larvae in the eastern Pacific Ocean
Canadian Journal
of Fisheries and
Aquatic Sciences
43: 1208-1213
Victor, BC (1986)
Delayed metamorphosis with reduced larval growth in a coral reef fish, Thalassoma bifasciatum
Victor, BC (1986) Marine Biology
90: 317-326
The duration of the planktonic larval stage of one hundred species of Pacific and Atlantic wrasses (Family Labridae)
Ecological Monographs
56: 145-160
Victor, BC (1986)
Larval settlement and juvenile mortality in a recruitment-limited coral reef fish population
Wellington, GM and Victor, BC (1985) Oecologia
68: 15-19
El Nino mass coral mortality: a test of resource limitation in a coral reef damselfish population
Limnology and Oceanography
29: 1116-1119
Victor, BC (1984)
Coral reef fish larvae: patch size estimation and mixing in the plankton
Victor, BC (1983) In: Reaka, ML, ed.
The ecology of deep
and shallow reefs.
US Dept of Commerce, DC

1983: 47-51
Settlement and larval metamorphosis produce distinct marks on the otoliths of Halichoeres bivittatus
Victor, BC (1983)
Recruitment and population dynamics of a coral reef fish
Victor, BC (1983) Marine Biology
71: 203-208
Daily otolith increments and recruitment in two coral reef wrasses, Thalassoma bifasciatum and Halichoeres bivittatus
Canadian Journal
of Zoology

60: 2543-2550
Victor, BC and Brothers, EB (1982)
Age and growth of the fallfish Semotilus corporalis with daily otolith increments as a method of annulus verification
Daily Otolith Increments and Recruitment in Two Coral-Reef Wrasses, Thalassoma bifasciatum and Halichoeres bivittatus. Benjamin C. Victor Department of Biological Sciences and Marine Science Institute, University of California at Santa Barbara; Santa Barbara, California 93106, USA Abstract Increments on the otoliths of two common coral reef fishes, the bluehead wrasse Thalassoma bifasciatum and the slippery dick Halichoeres bivittatus, were demonstrated by mark-recapture experiments to be daily. Otoliths were marked in two ways; by depriving fish of light, food, and temperature cycles and also by supplemental feeding in the field. Both experiments were performed in late 1980 in the San Blas Islands of Panama. A mark corresponding to settlement of the planktonic larva onto the reef was found on the otoliths of the bluehead wrasse. This settlement mark was used to calculate the dates of settlement of a collection of juveniles of this species taken from a patch reef in the San Blas Islands of Panama in 1981. Settlement occurred in short and irregular bursts. The number of daily increments before the settlement mark indicates a planktonic larval life of 40 to 72 d. Introduction Determining the age of tropical marine fishes, especially reef species, has traditionally been particularly difficult. Most methods of aging require that the fish undergo distinct annual cycles of growth leading to recognizable marks on the fish's hard parts, usually on scales, otoliths, bones, or spines. These cycles may occur in tropical estuarine environments (Fagade, 1974), but are, in general, absent in other tropical marine waters. As a result, little is known about the growth and survivorship of tropical reef fishes (Sale, 1980). Recently, however, daily increments on the otoliths of some fishes have been discovered (Panella, 1971). Otoliths are stone-like calcium carbonate accretions situated within the semicircular canals of bony fishes which assist in balance and sound perception. Increments on the otolith permit extremely precise determinations of the age of fishes. Increments that are assumed to be daily have been recorded on the otoliths of a variety of coral-reef fish species (Ralston, 1976; Panella, 1974, 1980; Brothers, 1979). In addition, interruptions and transitions corresponding to settlement, metamorphosis, spawning, and changes in life-history characteristics have been proposed (Brothers and McFarland, 1980; Panella, 1980). Unfortunately, the increments observed have not been clearly demonstrated to be daily. .Brothers (1979) has pointed out that there is a need for controlled field manipulations to validate this technique for tropical fishes and thus to encourage its widespread use. Since otolith increments are usually particularly distinct in juvenile fishes, this method of aging can be invaluable in studies of the early life history of reef fishes (Brothers, 1979). In the present study, I confirm that the increments on the otoliths of two Caribbean coral reef wrasses (the bluehead Thalassoma bifasciatum, and the slippery dick Halichoeres bivittatus) are indeed daily. I also demonstrate that a mark corresponding to the settlement of the planktonic larva onto the reef exists on bluehead wrasse otoliths. Furthermore, using this mark, I establish the age at settlement and the daily pattern of settlement onto the reef for this species. Both the daily pattern of settlement and the time spent in the plankton by larvae are important, yet largely unexplored, characteristic of the early life history of reef fishes. Sale (1980) has emphasized that further knowledge of the larval life of fishes and the details of recruitment are essential to an understanding of the processes determining community structure on coral reefs. The determinants of the rate and pattern of settlement onto reefs are yet unknown, despite the fact that the applicability of traditional community ecological theory depends on whether recruitment is controlled by factors within the resident community or not (Anderson et al., 1981). The distance of larval dispersal is also an important but unknown subject. According to both Sale (1980) and Anderson et al. (1981), the scale on which community ecological studies should be performed depends directly on the larval dispersal distance. The length of time larvae spend in the plankton is obviously an important determinant of the dispersal distance. Materials and Methods Daily Increments The most direct demonstration that increments on the otoliths of fishes in the field are daily is obtained by marking the otolith and subsequently comparing the number of increments between the mark and the edge with the number of days since the marking took place. If the increments are indeed daily, the number of increments after the mark should match the number of days since the marking occurred. I marked the otoliths of wrasses in two ways. In the first, I isolated groups of juvenile Thalassoma bifasciatum from all external stimuli for 4 d and then returned them to the reef. In the second, I supplementally fed a group of Halzchoeres bivittatus in the field for 5 d. The experiments were carried out in late 1980 on a large patch reef in the San Blas Islands on the Caribbean coast of the Republic of Panama (maps of the region are on p. 278 of Tribble, 1981). I captured 4 groups of juvenile bluehead wrasses (total n = 68) from the reef with an aquarium dipnet. Each group was immediately placed into a sealed insulated plastic container with about 10 liters of seawater. They were kept in the dark, unfed and undisturbed, for 4 d. At the end of this period I sacrificed some individuals from each group and returned the rest of the group to the reef. I released each group onto an isolated coral outcrop cleared of all resident bluehead wrasses. I used outcrops situated in seagrass beds behind the reef crest, which, in the San Blas Islands, are typical habitats for juvenile bluehead wrasses. Juveniles of this species have very restricted home ranges and tend to remain on the outcrop onto which they have settled (Victor, unpublished data). The 4 groups were recaptured from their outcrops after 8, 12, 18, and 26 d, respectively. Unmanipulated groups of bluehead wrasses were collected from surrounding outcrops before, during, and after the experiment. I marked the otoliths of slippery dicks by augmentation of food. First, I selected an area of shallow coral rubble and seagrass, about 2mx3 m that contained a resident population of about 20 juvenile fish. For each of 5 consecutive days I brought 20 sea urchins (Diadema antillarum) from a nearby reef and crushed them on the site. I observed that juvenile slippery dicks, as well as roving adults and other species, were quickly attracted and fed readily. On Days 1, 3, and 5, I added the urchins between 12.00 and 15.00 hrs; while on Days 2 and 4, I added them after 16.00 hrs. After 32 d I returned to the same site and caught all the resident juvenile slippery dicks. The juveniles of this species have very small home ranges (Victor, unpublished data). Unmanipulated juveniles were collected from the surrounding area before, during, and after the experiment. Settlement Mark Both Brothers and McFarland (1980) and Panella (1980) have suggested that marks corresponding to settlement can be found on some species' otoliths. To investigate the possibility of there being a settlement mark on the otoliths of bluehead wrasses, I collected juveniles on their first day of appearance on the reef. To do this I performed a daily census of the population of juvenile bluehead wrasses in an area of coral outcrops in a seagrass bed for several months in the summer of 1981. When new recruits were first seen on an outcrop that had had no juvenile bluehead wrasses resident for several weeks, the recruits were caught and immediately preserved in ethanol. Larvae that had not yet settled were captured in the plankton as they approached a light hung over the water at night. These larvae could be identified as bluehead wrasses by fin-ray counts. Daily Pattern of Settlement If there are daily increments on the otolith and a settlement mark, the date of settlement for any individual can be calculated by subtracting the number of increments between the settlement mark and the edge of the otolith from the known date of capture. To permit just such an analysis I collected a sample (n = 64) of juvenile bluehead wrasses (up to 30 mm standard length) from a large patch reef in the San Blas Island chain on 6 August 1981. All juveniles encountered were collected. Preparation of the Otoliths The lapilli and the sagittae, 2 of the 3 pairs of otoliths in teleosts, were removed from all of the wrasses collected. After removing the top of the cranium, I used a pair of fine forceps to extract the lapilli from the lateral walls of the brain case and the sagittae from beneath the posterior end of the brain. The otoliths were cleaned and placed in a drop of immersion oil on a glass microscope slide. These otoliths were then examined, without sectioning, under a compound microscope at magnifications ranging from 400 to 1 000~P.o larizing the transmitted light assisted greatly in clarifying the increments. Results Daily Increments All of the wrasses examined had distinct increments on both the lapilli and the sagittae. The counts made on one type of otolith always matched the counts made on the olher. Each increment is made up of a translucent line (light when examined with transmitted light) and a narrower opaque line (dark with transmitted light). Each Thalassoma bifasciatum captured at outcrops where experimental fish had previously been released (n=21) had a distinct mark on its otoliths. The mark was clearest on the lapilli, the snlaller of the two pairs of otoliths examined. Under the microscope the mark appears as a band which refracts light in a markedly different manner from that of the surrounding increments (Fig. 1). When in focus the band appears exceptionally light. At higher magnification it shows an absence of the usual light-dark alternating lines characteristic of normal otolith increments. A similar mark appeared at the edge of the otolith from individuals killed immediately after the isolation treatment and was never seen on any of hundreds of other untreated fish. In all 21 specimens, the number of increments between the mark and the edge of the otolith corresponded exactly to the number of days since the marked fish were released. A characteristic pattern was evident on the otoliths from all of the juvenile Halichoeres bivittatus larger than 25 mm caught at the former feeding site (n=10). The pattern was not on the otoliths of juveniles smaller than 25 mm. The pattern was made up of 5 unusually wide increments, surrounded by normally sized ones (Fig. 2). The second and fourth of these wide increments were not as wide as the other three. As in the case of the bluehead wrasses, the number of increments between the 5 wide increments and the edge of the otolith corresponded exactly to the number of days since the feeding was terminated. Seltlement Mark All bluehead wrasses captured on the reef, including large adults, had a conspicuous transition in the character of the increments near the center of the otolith (Fig. 3). The only bluehead wrasses not having this transition on their otoliths were larvae captured in the plankton (Fig. 4). Juveniles captured on their first day of appearance on the reef had this transition on the edge of their otoliths. At this transition, the previously prominent dark lines delineating each increment abruptly disappear. Regular increments only reappear after a band without discrete increments is formed. in the sample of 64 juvenile bluehead wrasses collected from a large patch reef, the number of visible increments between the nucleus of the otolith and the settlement mark ranged from 38 to 70 (mean of 46: SD=5.9). Daily Pattern of settlement Bluehead wrasses settle in short and somewhat irregular bursts (Fig. 5). Of the 64 juveniles taken from a large patch reef 34 had settled within a 2 d period. settlement appeared to be weakly correlated with the lunar cycle. Recruitment occurred primarily within the 2 wk around the new moon, although peaks of settlement did not fall directly on the new moon. All aging methods require validation before they can be used with confidence. Despite this obvious caveat, workers in the field of reeffish aging have liberally pursued analyses of otolith increments without first establishing their daily nature on any tropical reef species (see Panella, 1980). I believe it is an important first step to demonstrate, in the field, that the increments one observes are truly daily in both the species and age class under study. This is especially necessary in the light of recent proposals that there are often subdaily increments on the otoliths of tropical fishes (Brothers and McFarland, 1980; Panella, 1980). My results indicate that the increments on otoliths from juvenile Thalassoma bifasciatum and Halichoeres bivittatus are daily. In both mark-recapture experiments, the number of increments between the mark and the edge matched the number of days since the marking took place. Daily increments permit extremely precise determinations of age, especially of short-lived species that grow fast. Because of the previous lack of an effective aging method for tropical reef fishes, many details of their life histories have remained guesswork (Sale, 1980). At present no accurate life table, survivorship curve, or even direct longevity estimate is available for any species of tropical coral-reef fish. Clearly, the use of daily otolith increment aging will facilitate studies on these aspects of reef-fish ecology. This approach will also allow comparisons of growth and survival between different habitats and between different species; such comparisons should be of great importance to studies of competition, predation, and habitat selection by fishes in the coral-reef environment. The otolith-marking methods I used are simple and probably generally applicable to a wide spectrum of species. The isolation treatment deprived the subjects of all external influences such as light, food, temperature changes and currents. The fish undergoing the isolation treatment remained motionless and lay on their sides, presumably throughout the 4 d. Since wrasses do sleep at night, the treatment was in some ways equivalent to a 4 d long night. The isolation mark itself was a light band wider than the surrounding increments. If, as has been recently suggested, the light line in each light-dark couplet is laid down in the afternoon and at night, and the narrower dark line during the early part of the day, this isolation mark is exactly what one would expect to result from an abnormally long period of "night" growth (Mugiya et al., 1981; Tanaka et al., 1981; in contrast, Brothers and McFarland (1980) proposed that the dark line is laid down at night). Supplemental feeding is an even easier method of marking otoliths with a recognizable pattern. The isolation treatment requires capturing the subjects twice, and thus requires that the fish be hardy enough to withstand a few days of isolation and the handling involved. Supplemental feeding requires only that the subjects remain in the same place during the feeding and for some time afterwards. Most reef fishes, especially juveniles, are well known for their tendency to remain site-attached (Sale, 1980). The wider increments resulting from supplemental feeding indicate that the growth of the otolith is closely tied to the growth of the fish. This relationship may be very precise, since the increments corresponding to Days 1, 3, and 5 of the feeding experiment on juvenile slippery dicks were noticeably wider than those on Days 2 and 4. On Days 1, 3, and 5, I added urchins between 12.00 and 15.00 hrs and observed wrasses feeding on the debris for the rest of the afternoon. On Days 2 and 4, I added urchins after 16.00 hrs. Slippery dicks, along with many other grassbed fishes, tend to retreat for the night between 16.30 and 18.00 hrs each day. It is at this time of the evening that large predators such as barracuda and jacks are seen cruising the grassbeds. During these two feedings I noticed that the wrasses were particularly wary and, by 17.00 hrs were no longer feeding. Presumably the greater amount of food they obtained on Days 1, 3, and 5 had resulted in increased growth and thus relatively wider increments. Slippery dicks less than 25 mm standard length did not show any sign of a mark on their otoliths. Since the supplemental feeding took place over 1 mo before the capture, I believe these smaller juveniles either had not yet settled or were newly settled and too small to eat crushed urchins at the time of the feeding. It is not surprising that a transition in the character of the increments is associated with settlement in bluehead wrasses. Settlement and subsequent metamorphosis involve unusual and complex physiological changes. Transitions in otolith increment characteristics associated with shifts in habitat and feeding behaviors have been suggested for other species (Brothers and McFarland, 1980; Panella, 1980). The presence of the settlement mark permits one to determine the date and age of settlement of fishes collected long after they have settled. The pattern of settlement revealed by this technique showed that bluehead wrasses in the San Blas Islands settled in short and somewhat irregular bursts. This species spawns daily (Warner and Robertson, 1978), so the absence of a continuous "rain" of recruits can be ascribed to physical or biological processes occurring in the plankton. A strict lunar cycle of settlement was not evident, but settlement did appear to be concentrated within the 2 wk around new moon. Without the otolith technique, studies of the daily pattern of settlement are difficult and time-consuming. However, information on the pattern of settlement is essential to an understanding of what determines recruitment to a reef, and Anderson et al. (1981) have implied that if recruitment is determined by factors independent of the local resident community, traditional community ecological theory is inapplicable to reef-fish assemblages. Knowledge of the larval life of coral-reef fishes must be increased before we can adequately test views on the structure of reef-fish assemblages (Sale, 1980). A pivotal issue in the controversy over reef-fish community ecology is the extent of dispersal of pelagic larvae. The greater the distance of dispersal, the lesser the likelihood of local assemblages of reef fishes being in a stable equilibrium state (Anderson et al., 1981). Furthermore, the dispersal distance should determine the scale on which community ecology of coral-reef fishes should be examined (Sale, 1980; Anderson et al., 1981). Direct evidence of the length of time in the plankton is an obvious first step in the resolution of this controversy. Determining the length of the planktonic life of a species of fish is difficult without an accurate aging method. A few attempts have been made, most notably that of Randall (1961), who compared the timing of spawning with the timing of recruitment and came up with an estimate of 2.5 mo for the surgeonfish Acanthurus triostegus. Such determinations become much easier with the use of daily otolith increments. The number of increments between the nucleus of the otolith and the settlement mark ranged from 38 to 70 (with a mean of 46) in a sample of bluehead wrasses. The otoliths of wrasses first develop around the time of hatching, which, in the warm waters of the tropics, would be approximately 2 d after fertilization (Fritzche, 1978). Thus, the planktonic life of this species in the San Blas Islands of Panama appears to be on average 48 d, with a range of 40 to 72 d. Acknowledgements. This work was supported by NSF Grant DEB 78-23916 to Dr. R. Warner. I am especially grateful to Dr. R. Warner for his support and encouragement, and to Dr. E. Brothers for his guidance. I thank S. Schoen for assistance in the field, G. Wellington for help with the manuscript, and W. Haake for useful information. K. Clifton, M. Schildhauer, and G. Wellington provided helpful comments. I also thank the Smithsonian Tropical Research Institute and the Kuna Indians of the San Blas for making this work possible. Literature Cited Anderson, G. R. V., A. H. Ehrlich, P. R. Ehrlich, J. D. Roughgarden, B. C. Russell and F. H. Talbot: The community structure of coral reef fishes. Am. Nat. 11 7,476-495 (1981) Brothers, E. B.: Age and growth studies on tropical fishes. h: Proceedings of an International Workshop on Tropical Small- Scale Fishery Stock Assessment, held at the University of Rhode Island, September 1979. (Copies available from: Dr. E. B. Brothers. Section of Ecology and Systematics, Division of Biological Sciences, Cornell University, Ithaca, New York 14853, USA) Brothers, E. B. and W. N. McFarland: Correlations between otolith microstructure, growth, and life history transitions in newly recruited french grunts (Haemulon jlavolineatum (Desmarest), Haemulidae). In: Early life history of fish, 11. A Second International Symposium held in Woods Hole, 2-3 April 1979. Rapp. P.-v. Reun. Cons. perm. int. Explor. Mer 178,369-374 (1980) Fagade, S. 0.: Age determination in Tilapia melanotheron (Ruppell) in the Lagos Lagoon, Lagos, Nigeria. In: Ageing of fish, pp 71-77, Ed. by T. B. Bagenal. Old Woking, Surrey: Unwin Brothers 1974 Fritzche, R. A,: Development of fishes of the Mid-Atlantic Bight, Vo1.5. 340 pp. Washington D.C.: U.S. Department of the Interior 1978 Mugiya, Y., N. Watabe, J. Yamada, J. M. Dean, D. G. Dunkelberger and M. Shimuzu: Diurnal rhythm in otolith formation in the goldfish, Carassius auratus. Comp. Biochem. Physiol. 68A, 659-662 (1981) Panella, G.: Fish otoliths: daily growth layers and periodical patterns. Science, N.Y. 173, 24-27 (1971) Panella, G.: Otolith growth patterns: an aid in age determination in temperate and tropical fishes. In: Ageing of fish, pp 28-39. Ed. by T. B. Bagenal. Old Woking, Surrey: Unwin Brothers 1974 Panella, G.: Growth patterns in fish sagittae. In: Skeletal growth of aquatic organisms, pp 519-560. Ed. by D. C. Rhoades and R. A. Lutz. New York: Plenum Press 1980 Randall, J. E.: A contribution to the biology of the convict surgeonfish of the Hawaiian Islands, Acanthurus triostegus sandvicensis. Pacif. Sci. 15, 2 15-272 (196 1) Ralston, S.: Age determination of a tropical reef butterflyfish utilizing daily growth rings of the otoliths. Fish. Bull. U.S. 74,990-994 (1976) Sale, P. F.: The ecology of fishes on coral reefs. Oceanogr. mar. Biol. A. Rev. 18, 367-421 (1980) Tanaka, K., Y. Mugiya and J. Yamada: Effects of photoperiod and feeding on daily growth patterns in otoliths of juvenile Tilapia nilotica. Fish. Bull. U.S. 79, 459-466 (1981) Tribble, G. W.: Reef-based herbivores and the distribution of two seagrasses (Syringodium jliforme and Thalassia testudineum) in the San Blas Islands (Western Caribbean). Mar. Biol. 65, 277-281 (1981) Warner, R. R. and D. R. Robertson: Sexual patterns in the labroid fishes of the western Caribbean. I: The wrasses (Labridae). Smithson. Contr. Zool. 254, 1-27 (1978) Age and growth of the fallfish Semotilus corporalis with daily otolith increments as a method of annulus verification BENJAMIN C. VICTOR Department of Biological Sciences and Marine Science Institute, University of California, Santa Barbara, CA, U.S.A. 93106 EDWARD BROTHERS Section of Ecology and Systematics, Division of Biological Sciences, Cornell University, Ithaca, NY, U.S.A. 14853 Received December 4, 198 1 VICTOR, B. C. and E. B . BROTHERS 1982. Age and growth of the fallfish Semotilus corporalis with daily otolith increments as a method of annulus verification. Can. J. Zool. 60: 2543-2550. Daily increments were found in the otoliths of the fallfish Semotilus corporalis from three stream populations in central New York. By counting these increments one can verify annual marks and validate other less precise methods of aging. Results suggested that a false first annulus was observed in the only previous study of fallfish age and growth. Annual growth in length is shown to be linear. All three populations' growth rates were significantly different. Furthermore, the difference among these local populations can account for much of the variability in the rate of growth exhibited throughout the species' range. It is therefore proposed that the nature of the local habitat, in particular the size of the stream and the density of conspecifics, may be the major determinant of the rate of growth in the fallfish. Introduction Determining the age of fishes depends primarily on periodicity in the growth history of the fish. This periodicity is detectable in the fish's hard parts, such as scales, otoliths, bones, and spines. Before the past decade all methods of aging were limited in their resolution to annual or seasonal periods. There are two major problems associated with this level of resolution. The first is that the fish must undergo distinct annual or seasonal cycles of growth for recognizable marks to be formed on their hard parts. Tropical, larval, and 1st-year fishes are all difficult to age because of this problem. The second problem is not one of feasibility but one of accuracy and precision. Estimating the age of a fish in years by use of a method which, at its finest resolution, consists of counting annual marks, subjects the estimate obtained to a wide degree of error; in short, one unit miscounted results in the age estimate being an entire year astray. Furthermore, there is a general lack of verification of age determinations for all age classes in the stock. Lately, a series of papers concerning errors in the aging of fishes have underscored the problem. The causes usually cited are false annuli, hidden or missing annuli, and misinterpreted spawning or metamorphic marks (e.g., Bearnish 1979; Carlander 1974; Linfield 1974; Williams and Bedford 1974). Recently, however, the situation has improved with the discovery of daily incremental marks on the otolith by Panella (1971). Otoliths are calcium carbonate accretions situated in the semicircular canals of bony fishes which assist in balance and sound perception. These marks can help to verify the ages of young individuals (Brothers et al. 1976; Brothers 1980; Brothers and McFarland 1980; Struhsaker and Uchiyama 1976; Taubert and Coble 1 977), and, in some fishes, are the only way of routinely aging populations (e.g. the tropical wrasse, Thalassoma bifasciatum, B. C. Victor, in preparation). Furthermore, by counting the number of daily increments between successive annual marks one can verify both the number and position of these annuli. In this way the technique allows for a remarkably fine level of resolution both for validating age determina- aging using this method alone. In this study we used daily otolith increments to age three local populations of the fallfish Semotilus corporalis. The fallfish is the largest native Eastern cyprinid and ranges from Ontario south to Virginia (Scott and Crossman 1973). The life history of the fallfish has been previously documented by Reed (1971), who used scale annuli for aging. We shall, however, demonstrate that in his study a false first annulus was probably observed and, as a result, the age and growth profile of this species has been misrepresented. A revised profile shows the growth of fallfish to be remarkably linear. In addition, the variation in growth rates between populations appears to be accounted for by local habitat differences unrelated to latitude. Materials and methods Approximately 100 fallfish were collected from each of three streams in the vicinity of Ithaca, New York. The three streams were Willseyville Creek in the town of Willseyville, Catatonk Creek in the town of Candor, both in Tioga County, and Fall Creek in the town of Ithaca in Tompkins County. All three sampling sites are within a radius of 20 km around Willseyville in southern central New York State. The two former streams are in the Susquehanna River drainage while Fall Creek is part of the Finger Lakes - Great Lakes drainage. Fish were captured by a combination of seining, angling, and electrofishing and were weighed, measured (TL), and sexed while fresh or after being frozen. The collections were all made during the late fall of 1978 and early spring of 1979. Our aim was to collect the fish while the otolith was no longer growing, i.e. during the formation of the annual winter mark. Preliminary observations of the dates of cessation of otolith growth in fall and its resumption in spring showed that most of the collections were made within the period of winter mark formation, while a few fell at most 1 or 2 weeks beyond the limits. Both fall and spring collections were made at each of the collection sites. We obtained the utricular otoliths, or lapilli, from each fish by cutting horizontally through the cranium which exposed the brain. The pair of lapilli, lying just lateral to the optic lobes, were removed with fine forceps, cleaned, and placed in a drop of immersion oil on a glass slide. A sample of scales was also taken. Preparation of the otolith followed the procedure outlined in Brothers et al. (1976). The fallfish lapillus, being somewhat ovoid, was ground on both of the flatter sides until a section roughly 1 mrn thick remained. Grinding was done by hand on a glass plate with Carborundum 600 grit in oil. The section thus obtained included the nucleus and was sufficiently translucent to allow examination with transmitted light. The otolith was then returned to the immersion oil and viewed under a compound microscope at magnifications ranging from 400 to 1000X. All measurements of length on the otolith were from the nucleus out along the longest radius of the section. The shape of the otolith and the position of the longest radius were notably constant for all individuals examined. The number of fine increments visible on each otolith was counted. The count was begun at the nucleus and progressed outwards in the direction of the longest radius. The number of increments was recorded on a Clay Adams multiple register hand counter, and as each prospective annual mark was encountered the tally was continued on a new register. On completion of the count, the age in years was recorded (the number of annuli encountered plus the one at the edge of the otolith). In order to verify that the increments we observed were actually daily ones, we raised a cohort of fallfish in the lab. Eggs were collected from newly built fallfish nests in Willseyville Creek during May 1979. The eggs and young fish were maintained in a temperature-controlled flow-through tank with a temperature cycle corresponding to that in the stream. Otoliths first appeared around the time of hatching, about 5 days after fertilization, and for 2 weeks thereafter individuals were killed each day and their otoliths were examined. We also captured young-of-the-year from the same stream during June . and July and counted the number of increments on their otoliths. Lastly, we captured older fish at different times throughout the growing season and counted the number of increments between the last winter mark on the otolith and the edge. Results and discussion Age determination It is generally accepted in the literature that the term otolith is synonymous with sagitta, or the saccular otolith, primarily because all past work on aging by otoliths has been done with the sagitta (Taubert and Coble 1977; Panella 1980). However, in the fallfish and probably in all cyprinids, the sagitta is not useful for age determination because it shows no clear marks. The lapillus, or utricular otolith, should be used instead. Consequently, in this discussion, we shall use the term otolith to refer to the lapillus. It has been known for a long time that the otoliths of some fishes have annuli. An annulus viewed without high magnification consists merely of the transition from a translucent band to one that is opaque. With increased magnification, however, these bands resolve into a multitude of fine lines. On the otolith of the fallfish they are particularly apparent. At this magnification, the annulus is visible as an interruption in the usual sequence of increments just before the start of the . opaque band. It can be recognized as a discontinuity preceded by increasingly fine, light increments and followed, further out along the radius, by progressively - larger and darker ones (Fig. 1). The area of fine increments corresponds to the "hyaline" (or translucent) zone, and the larger, darker increments correspond to the "opaque" zone of classical otolith reading under low magnification. The general interpretation is that the translucent band is formed during the slow or no growth period in the fall and winter and the opaque one during spring and summer (Blacker 1974). The annulus, or winter mark, was found at the edge of otoliths from fallfish captured in early spring and had not yet formed at the edge of otoliths from those captured in the early fall. Increments such as thesc on other species' otoliths have been shown to be daily. Panella (1971) counted the rings on hake Merluccius productus otoliths and found . . an average of 360 per year. Brothers el al. (1976), Struhsaker and Uchiyama (1976), and Tauberl and Coble (1977) demonstraied experimentally that the number of increments on otoliths of laboratory-raised fish corresponded with their age in days. In our laboratory-raised fallfish we found that otoliths first formed around the time of hatching and for the next 2 weeks a new increment was laid down each day. Young-of-the-year fallfish captured during their first sumnler showed an increasing number of increments as the season progressed and this number corresponded wilh the number of days since the hatching period for the population, In Willseyville Creek in 1979 I first observed nests at the beginning of May. Juvenile fallfish captured there on June 26 had an average of 58 increments on their otoliths (n = 25). while juveniles captured on July I8 had an average of 74 increments on their otoliths (n = 25) (corresponding overall to a hatching date of May I). Older fish showed a similar pattern of increasing numbers of increments between rhe last annulus and the edge of the otolith as the season progressed. In fact, by counting back from the date of capture, one can calculate when the first increments after the annulus were laid down. In a series of older fish captured late in the season from Willseyville Creek in 1978 (n = 8), the count revealed [hat [he first increment was laid down in early May. After the 1st week of October of that year all of the fish captured from the three streams had the annulus forming on the very edge of rlleir otoliths. Total increment counts between successive annuli for all ages generally matched this 5-month season. These counts ranged from 110 to 154 and showed no significant tendency to diminish with age: the mean total count per year for successive age-classes were 13 1 (n = 13), 133 (n = 20), 129 (n = 5), 129 ( 1 1 = 5), 122 (n = 5), 125 (n = 3), 122 (n = 3), 126 (n = I), 129 (n = I). On thc majority of otoliths annuli were relatively easy to identify at low magnification, in contrast to fallfish scales which are often hard to read (Fig. 2). In some older fish, however, the difference in opacity between the translucent and opaque zones was diminished (Fig. 3) and decisions whether an annulus existed or not became more subjective. Also, because the core of the otolith (laid down during the first season of growth) is relatively more opaque, decisions on where the first amulus was were difficult. These problems were a product of the criterion used for annulus identification at low magnification, i.e. a transition from a translucent zone to one that is opaque. At high magnification, when the criterion for an annulus is a discontinuity preceded by increasingly narrow increments and followed by increasingly wide ones, no such problems were present. We found no aberrant counts of increments between successive annuli, which had they existed, would have implied false annuli and required independent methods of validation. The daily otolith increment method of aging is sufficient for aging all age-classes of fallfish; however, its most useful application is for verifying more easily used techniques. The technique is especially valuable for validating the the juvenile fallfish captured by Reed (up 10 69 mm TL) led him to search for a hidden first annulus on fallfish scales, which he subsequently found (R. J. Reed, personal communication). However, our examination of the otoliths of all the large juvenile fallfish that we captured (up to 82 mm TL) showed that they were indeed young-of-the-year. None had more than 143 daily increments, and these were regular and uninterrupted. No sign of any unusual increment panern corresponding to Reed's supposed first annulus was found. Furthermore, in his study [he increase in length In the "2nd" year was about half that of any other year of the fish's life, leading to an implausibly dented growth curve. Individuals in their "1st" year were found in only two of the eight streams examined (Reed 1972). Based on these facts, we believe Reed's first annuIus was a false annulus, and the groups of fish he designated as 1st and 2nd year fish do not constitute different age-classes but were, in fact, all 1st-year fish. Growth The growth curves of the three fallfish populations were linear (no significant departure from linear regression; Snedecor and Cochran 1967) (Fig. 4). Comparisons of the regression coefficients indicated that the Fall Creek population grew faster than the Calatonk Creek population, which, in turn, was faster growing than the Willseyville Creek population (p< 0.025 and p< 0.001, respectively) (Table 1). After relatively fast growth the first season, additional increases in length stay somewhat constant without much leveling off characteristic of many other fish growth curves. On the Walford graph of the fallfish data a line virtually parallel to the diagonal is obtained (Fig. 5) (method described in Ricker 1975). Ricker reports a similar line is characteristic of some long-lived cool water fish, but its occurrence in a minnow is unusual. This linearity is probably not an artifact of incomplete collections (i.e., missing the older fish who are presumably slower growing) since the two 9-year-old fish we have captured (no fallfish exceeding 9 years old has been found in any study to date) fall close to the lines in Fig. 4. It is, however, possible that if a large sample of very old individuals were obtained the growth curve would begin to level off. Reed (197 1) reports that males exceed females in size after 3 years but even at 4 years of age we found no significant differences in size in any stream: in Willsey- ville Creek, the mean TL of 4-year-old females was 179.9 mm vs. 178.1 mm for males (n = 19 and 11, respectively); in Catatonk Creek, females 201.6 mm vs. males 200.4 mm (n = 20 and 14); in Fall Creek, females 226.3mm vs. males 231.2mm (n= 7 and 20). Longevity did not seem to vary among the populations of fallfish studied. Individuals 9 years of age, the oldest yet recorded, have been captured from both fast and slow growing populations. Both 9-year-olds were females; however, there is not enough evidence to state whether longevity is different for males and females. In this paper we have avoided using back-calculation with its usual loss of precision. This method estimates the length of an individual at a past annulus by using the radius of the scale or otolith. The annuli on fallfish otoliths are, nevertheless, quite suitable for back-calculation, since the relationship between total length and otolith radius is quite consistent (Fig. 6). The differences between the three streams in the growth rate of fallfish are clearly not a result of latitudinal differences. All three collecting sites were within 20 km of the town of Willseyville in central New York. In previous studies of growth in various Semotilus species, growth rates were compared over the geographiical range of the species, and latitude (with its concomitant changes in the length of the growing season) was considered a particularly important determinant of growth (Powles et al. 1977; Stasiak 1978; Reed 1971). There was little emphasis on the effect of differing habitat types and Powles et al. (1977) even suggested that growth was independent of the habitat type in Semotilus atromaculatus. A comparison of Reed's (1971) results with ours can clarify the relative influences of habitat type, latitude, and year to year differences on fallfish growth rates. Reed's eight collection sites ranged from New Brunswick to Pennsylvania and included a reservoir in Massachusetts. His collections also date back as far as 1953. Nevertheless, in the first two age-classes, the range of mean size of our local populations overlaps the entire range of mean size for those ages reported by Reed (Fig. 4). Furthermore, in subsequent age-classes , the differences in mean size of our local populations encompass much of the range found in Reed's study. The fact that so much of the variability in growth rate evident among Reed's disparate populations can be matched by three local stream populations in the center of the species' range suggests that local habitat differences are the primary determinant of the rate of growth in fallfish. The most apparent difference between the three sites was the size of the stream. The Willseyville Creek collections (exhibiting the slowest growth) were made along a 100-m stretch of the stream with an average width of about 3 m and a greatest depth of less than 1 m. The fish from Catatonk Creek were taken from a 500-m section of the stream where the mean width was about 10 m and the maximum depth about 1.5 m. The Fall Creek collections required a several kilometre length of stream to obtain the desired sample size where the average width was about 12 m and the depth ranged up to several metres. Fall Creek has a drainage area of 10412 ha, Catatonk Creek has one of 6864 ha, and Willseyville Creek has a drainage area of less than half that of Catatonk Creek (Dunn 1970). Since collecting was continued until 100 individuals were captured in each stream, the area and effort required are some indication of the density of fallfish. Both the area and the effort expended per unit area increased greatly with stream size. Despite some lessening of capture efficiency in larger streams, we believe that the density of fallfish was inversely related to the size of the stream. Apparently the combination of large stream size and low density of fallfish was a major contributor to growth, perhaps through moderated temperatures or increased food supply. Further investigation of the specific features of the local habitat that determine growth rate is necessary for a comprehensive understanding of the pattern of variability in the growth of this and other species. Acknowledgements The help in statistics by Dr. A. Stewart-Oaten, J. Bence, and M. Schildhauer is appreciated as is the assistance of S. Cooper, W. Haake, W. Tom, P. Tsang, and E. Volk who assisted the senior author in collecting. We thank G. Robinson, M. Schildhauer, Dr. R. Warner, and Dr. G. Wellington for their constructive comments on the manuscript as well as Dr. John Heiser for his truly contagious enthusiasm for fishes and biology. Dr. R. Beamish and an anonymous reviewer provided especially helpful comments on the manuscript. BEAMISH R,. J. 1979. Differences in the age of Pacific hake (Merlucciusproductus) using whole otoliths and sections of otoliths. J. Fish. Res. Board Can. 36: 141-151. BLACKER R., W. 1974. Recent advances in otolith studies. In Sea fisheries research. Edited by F. R. Harden Jones. John Wiley and Sons, New York. pp. 67-90. BROTHERS, E B, . 1980. What can otolith microstructure tell us about daily and subdaily events in the early life history of fish? Rapp. P. V. Reun. Cons. Int. Explor. Mer, 178: 393-394. BROTHERS E,. B., C. P. MATHEWSa,n d R. LASKER1. 976. Daily growth increments in otoliths from larval and adult fishes. Fish. Bull. 74: 1-8. BROTHERS E.,B ., and W. N. MCFARLAND19. 80. Correlations between otolith microstructure, growth, and life history transitions in newly recruited french grunts (Haemulon jlavolineatum (Desmarest), Haemulidae). Rapp. P. V. Reun. Cons. Int. Explor. Mer, 178: 369-374. CARLANDER., D . 1974. Difficulties in ageing fish in relation to inland fisheries management. In Ageing of fish. Edited by T. B. Bagenal. Unwin Brothers, Old Woking, Surrey. pp. 200-205. DUNN, B. 1970. Maximum known stages and discharges of New York streams. N.Y. Water Resour. Cornm. Bull. No. 67. LINFIELD R, . S. J. 1974. The errors likely in ageing roach Rutilus rutilus (L.), with special reference to stunted populations. In Ageing of fish. Edited by T. B. Bagenal. Unwjn Brothers, Old Woking, Surrey. pp. 167-172. PANELLA G, . 1971. Fish otoliths: Daily growth layers and periodical patterns. Science (Washington, D.C.), 173: 1124-1126. 1980. Growth patterns in fish sagittae. In Skeletal growth of aquatic organisms. Edited by D. C. Rhoades and R. A. Lutz. Plenum Publishing Corp., New York. pp. 519-560. POWLES P, . M., D. PARKERa, nd R. REID. 1977. Growth, maturation, and apparent absolute fecundity of creek chub, Semotilus atromaculatus (Mitchill), in the Kawartha Lakes region, Ontario. Can. J. Zool. 55: 843-846. REED, R. J. 1971. Biology of the fallfish, Semotilus corporalis (Pisces, Cyprinidae). Trans. Am. Fish. Soc. 100: 7 17-725. RICKER, W. E. 1975. Computation and interpretation of biological statistics of fish populations. Bull. Fish. Res. Board Can. 191: 1-382. SCOTT W, . B., and E. J. CROSSMAN. 1973. Freshwater fishes of Canada. Bull. Fish. Res. Board Can. 184: 1-966. SNEDECOR G,. W., and W. G. COCHRAN 1967. Statistical methods. Iowa State University Press, Ames, IA. STASIAK R,. H. 1978. Food, age, and growth of thepearl dace, - .I Semotilus margarita, in Nebraska. Am. Midl. Nat. lOO(2): 463-466. STRUHSAKER.,P, and J. H. UCHIYAMA. 1976. Age and - growth of the nehu, Stolephorus purpureus (Pisces: Engraulidae), from the Hawaiian Islands as indicated by daily growth increments of sagittae. Fish. Bull. 74: 9-17. TAUBERT B,. D., and D. W. COBLE. 1977. Daily rings in the otoliths of three species of Lepomis and Tilapia mossambica. J . Fish. Res. Board Can. 34: 332-340. WILLIAMS T,. , and B. C. BEDFORD. 1974. The use of otoliths for age determination. In Ageing of fish. Edited by T. B. Bagenal. Unwin Brothers, Old Woking, Surrey. pp. 114-123.