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Home , Bothidae, Hornyhead turbot, Pleuronectidae, Pleuronichthys, Turbot

Aspects of the Life History of Hornyhead , verticalis, off Southern California

he T(Pleuronichthys verticalis) is a common resident on the mainland shelf from Magdalena Bay, Baja Califor- nia, Mexico to Point Reyes, California (Miller and Lea 1972). They are randomly distributed over the bottom at a density of about one per 130 m2 and lie partially buried in the sediment (Luckinbill 1969). Hornyhead turbot feed primarily on sedentary, tube-dwelling (Luckinbill 1969, Allen 1982, Cross et al. 1985). They pull the tubes from the sediment, Histological section of a fish ovary. extract the , and then eject the tube (Luckinbill 1969). Hornyhead turbot are Orange County, p,p’-DDE Despite the importance of batch spawners and may averaged 362 μg/kg wet the hornyhead turbot in local spawn year round (Goldberg weight in hornyhead turbot monitoring programs, its life 1982). Their planktonic eggs liver and 5 μg/kg dry weight in history has received little are 1.00-1.16 mm diameter the sediments (CSDOC 1992). attention. The long-term goal (Sumida et al. 1979). Their In the same year in Santa of our work is to determine larvae occur in the nearshore Monica Bay, p,p’-DDE aver- how a relatively low trophic plankton throughout the year aged 7.8 mg/kg wet weight in level fish like the hornyhead (Gruber et al. 1982, Barnett et liver and 81 μg/kg dry weight turbot accumulates tissue al. 1984, Moser et al. 1993). in the sediments (City of Los levels of chlorinated hydrocar- Several agencies in South- Angeles 1992). The highest bons several orders of magni- ern California measure the tissue levels of chlorinated tude greater than levels in bioaccumulation of trace hydrocarbons in hornyhead sediments. The objectives of metals and chlorinated hydro- turbot occur on the Palos this study were to describe carbons in muscle tissue of Verdes Shelf; concentrations the reproductive cycle and hornyhead turbot as part of decline to the north and south diet of Pleuronichthys their receiving water monitor- (Mearns et al. 1991). verticalis on the mainland ing programs. In 1991 off shelf off Orange County.

154 Fish weight-length relation- reproductive status. Male Materials and Methods ships were calculated sepa- gonads were rated based on rately for males and females the system of Grier (1981) Hornyhead turbot were from: and female gonads were rated collected off Huntington W = aLb, based on the system of Ross Beach in 30-35 m of water where: and Merriner (1983) (Table 1). approximately every six weeks W = body weight in gm and The diameters of a minimum in 1992 (Figure 1). Fish were L = standard length in cm. of 50 randomly selected collected with a 7.6 m The constants a and b were oocytes were measured for headrope otter trawl in the determined by nonlinear re- each female in a subset of morning and transported live gression technique (Marquardt females from each collection. to the laboratory. The fish 1963) in Sigmaplot™ for Only oocytes sectioned were euthanized with MS- Windows Version 1.00. through the nucleus were 222, measured to the nearest The gonadosomatic index measured. mm standard length, and (GSI) was calculated for indi- The stomach contents and weighed to the nearest 0.1g. vidual fish from: major taxa were weighed to

The stomachs were removed, GSI (%) = (WG/ WB) X 100, the nearest 0.01 g. Prey placed in Davidson’s fixative where: items were identified to the for 30 days, and then trans- WG = gonad weight in gm lowest possible taxon. The ferred to 70% ethanol. The and Index of Relative Importance gonads were removed, WB = body weight in gm. (IRI) modified from Pinkas et weighed, and a 1-2 mm sec- Sections of gonads were al. (1971) was calculated tion was removed from the cut at 6 μm and stained in from : center and placed in hematoxylin and eosin. The IRI = %O (%N + %W), Davidson’s fixative for 30 histological preparations of where days. the gonads were evaluated for %O = percent occurrence, %N = percent numbers, and %W = percent weight. Figure 1. The sample size of stomachs Map of the study area off Orange County. that was sufficient to describe the diet of hornyhead turbot was determined from a plot of cumulative taxa versus num- ber of stomachs. The asymp- tote of the curve was the minimum sample size. The diel feeding pattern was determined from fish collected throughout a 24 h period in November 1992. Fish were collected by trawl- ing before and after sunrise and sunset, and around mid- day and midnight. The fish were measured, sexed, and dissected on the ship. The stomachs were placed in

155 Table 1. Reproduction Females reached sexual Rating system for female and male Plueronichthys verticalis gonads. maturity at 150-160 mm SL STAGE FEMALES MALES (Figure 3). The GSI for mature females was high (>3%) from I Immature: Ovigerous lamellae Immature: January to September (Figure composed of dense aggregations Spermatogonial of undifferentiated oogonia and proliferation. 4). More females with stage primary oocytes. four and five oocytes were collected between January II Resting: Primarily early and Early recrudescence: previtellogenic oocytes with <1% Spermatogonia and and March (Figure 5) and the early vitellogenic oocytes. spermocytes present. largest oocytes occurred in March. Ripe and running III Developing: Previtellogenic Mid-recrudenscence: All oocytes numberically dominant with stages of sperm females (stage 6) were not some early and active vitellogenic development present. collected during the study. oocytes. Males reached sexual matu- rity at 90-100 mm SL (Figure IV Well developed: Vitellogenic Late recrudescence: oocytes predominant and evenly Tubules filled with 6). The GSI for mature males distributed over a large range sperm and number of was highest between July and developing cysts are September (Figure 7). Males declining. with sperm (stage 5) were V Ripe: Broad distribution of Functional maturity: collected between October vitellogenic oocyte, with a mode of Tubules filled with and January (Figure 8). very large vitellogenic oocytes with sperm, very little, if some atresia. any spermatogenisis is occurring. Food Habits The plots of cumulative VI Spent: No evidence of Post spawn taxa became asymptotic at vitellogenisis, stage IV and V oocytes are atretic, a few stage III about 40 stomachs in the oocytes occur. annual study and in the 24 h study (Figure 9). Hornyhead turbot fed on bivalves and Davidson’s fixative and polychaetes almost exclu- treated as before. Individual sively (Table 2). Bivalves fish weight was estimated Results composed 44% of the total from a weight-length regres- IRI in the annual study and sion for males and females Size 57% in the 24 h study. Poly- previously collected. The The relationship between chaetes composed 56% of stomach contents weight was length and weight was differ- the total IRI in the annual normalized to fish weight ent for females and males study and 40% in the 24 h from: (Figure 2). Females weighed study. ate only the more than males at the same WNS = (WS / WB) X 100, tip of the bivalve siphon and where: length and also grew to a not the whole bivalve. Solen larger size than males. The WNS = normalized stomach roseaceous was the most contents weight, weight-length relationships common bivalve in the diet. W = stomach contents were: Polychaetes were generally S 2.145 weight, and females W = 0.3027 L consumed whole. Diopatra W = fish body weight and ornata, Pista alata, and B 1.767 predicted from regression. males W = 0.8915 L . Paraprionospio pinnata were

156 the most frequently occurring polychaetes. , Figure 2. Weight-length regression for female and male Pleuronichthys nemerteans, nematodes, and verticalis off Orange County. cnidarians were also con- sumed, but made up less than 3% of the total IRI. Hornyhead turbots had diel 500 and annual feeding patterns. In the 24 h study, fish col- FEMALES 400 MALES lected around sunrise had the highest stomach contents weight, which declined to a 300 low in the evening (Figure 10). In the annual study, the 200 median stomach contents WEIGHT (G) weight of fish collected in the 100 summer (2.64 g) was more than double the weight of fish 0 collected in the winter (0.98 50 100 150 200 250 300 g). STANDARD LENGTH (MM) Discussion

Males and females grew at Figure 3. the same rate up to about Stage of development of female Pleuronichthys verticalis by 150 mm, about the size of size class. sexual maturity. After 150 mm, females grew proportion- STAGE 1 STAGE 2 STAGE 3 ately more than males. STAGE 4 STAGE 5 STAGE 6 Hornyhead turbot appeared to spawn mainly from late winter 100 to spring, but Goldberg (1982) suggested that they spawn 80 through the year. Their larvae occur in the plankton all year, 60 but abundance is highest between June and August 40

with a smaller peak between PERCENT February and April (Moser et 20 al. 1993). The larvae occur predominately inshore (Gruber et al. 1982, Moser et al. 0 1993) in depths between 5-

70 m (Barnett et al. 1984). 80-89 90-99 We found the largest concen- 100-109 110-119 120-129 130-139 140-149 150-159 160-169 170-179 180-189 190-199 200-209 210-219 220-229 230-239 240-249 250-259 260-269 270-279 280-289 trations of hornyhead adults STANDARD LENGTH (MM)

157 and juveniles off Huntington Figure 4. Beach in 30-35 m of water. Stage of development of male Pleuronichthys verticalis size class. Spent males were collected in January, but spent females were not encountered during

STAGE 1 STAGE 2 STAGE 3 the study. These results were similar to Goldberg (1982) STAGE 4 STAGE 5 STAGE 6 who found that 93% of the 100 females he examined (n=140) had mature oocytes, but only 80 3% had postovulatory follicles (evidence of recent spawn- 60 ing). It is also possible that the El Niño that occurred in 40 1992 with the accompanying PERCENT elevated water temperatures (CSDOC 1992) affected the 20 reproductive ability of hornyhead turbot. 0 Hornyhead turbot had a diet restricted primarily to 80-89 90-99 bivalves and tube-dwelling 100-109 110-119 120-129 130-139 140-149 150-159 160-169 170-179 180-189 190-199 200-209 210-219 220-229 230-239 240-249 polychaetes; other taxa were STANDARD LENGTH (MM) probably eaten incidentally. Interestingly, the cnidarian, Ceriantheria sp., occurred in 7% of the fish collected dur- Figure 5. ing the 24-h study. It is a Mean maximum oocyte diameter (± S.E.) for female tube-dwelling anemone that Pleuronichthys verticales by month. probably resembles tube- dwelling polychaetes (Morris et al. 1980). Hornyhead 0.6 turbot examined by Luckinbill (1969), Allen (1982), and 0.5 Cross et al. (1985) also ate relatively few species of tube- 0.4 dwelling polychaetes; bivalves were not an important prey 0.3 item in these studies. 0.2 Hornyhead turbot fed pre- dominately at sunrise. Food 0.1 availability was probably higher in the summer when 0.0 fish contained about three JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC MAXIMUM OOCYTE (MM)DIAMETER times the mass of prey as fish MONTH collected in the winter. The diets of fish caught in the

158 annual and 24 h studies were Figure 6. nearly identical. Because of Stage of development of female Pleuronichthys verticalis by the narrow dietary range, 40 month. stomachs were sufficient to describe the food habits.

Conclusions

STAGE 1 STAGE 2 STAGE 3 The hornyhead turbot is a STAGE 4 STAGE 5 STAGE 6 common resident of the main- 100 land shelf off Southern Cali- fornia. It is a small mouth 80 flatfish that preys on bivalves and polychaetes, which in turn are primarily deposit and 60 suspension feeders. If bioaccumulation is primarily PERCENT 40 through the food, the foodweb leading to hornyhead 20 turbot is relatively simple. Future studies will focus on 0 how contaminants are trans- JAN MAR MAY JUL SEP OCT DEC ferred from particles to MONTH bivalves and polychaetes and then to turbots.

Figure 7. Mean gonadosomatic index (GSI) for Pleuromichthys verticalis A) males >120 mm and B) females >150 mm (± S.E.) by month.

AB0.28 6 0.24 5 0.20

0.16 4

0.12 3 GSI (%) GSI (%) 0.08 2 0.04

0.00 1

L R N T V PR AY AR P C EC JAN FEB MAR A M JUN JU AUG SEP OCT NOV DEC JAN FEB M A MAY JU JUL AUG SEP O NO D MONTH MONTH

159 Figure 8. References Stage of development of male Pleuromichthys verticalis by month. •Allen, M.J. 1982. Functional structure of soft-bottom fish communities of the Southern STAGE 1 STAGE 2 STAGE 3 California Shelf. Ph.D. Diss., STAGE 4 STAGE 5 STAGE 6 University of California, Scripps 100 Institution of Oceanography. 577 pp. •Barnett, A.M., A.E. Jahn, P.D. 80 Sertic, and W. Watson. 1984. Distribution of ichthyoplankton of 60 San Onofre, California, and meth- ods for sampling very shallow coastal waters. Fish. Bull. 82:97-

PERCENT 40 109. •City of Los Angeles. 1992. Marine 20 monitoring in Santa Monica Bay: Annual assessment report for the 0 period July 1990 through June JAN MAR MAY JUL SEP OCT DEC 1991. Environmental Monitoring Division, Bureau of Sanitation, City MONTH of Los Angeles. 225 pp. •County Sanitation Districts of Orange County. 1992. Marine monitoring. Annual report 1992. County Sanitation Districts of Orange County, Fountain Valley, Figure 9. California. Plots of the cumulative number of taxa consumed by •Cross, J.N., J. Roney, and G.S. Pleuromichthys verticalis in the annual and 24 h studies off Orange Kleppel. 1985. Fish food habits County. along a pollution gradient. Calif. Fish Game 71:28-39. •CSDOC see County Sanitation 50 Districts of Orange County. •Goldberg, S.R. 1982. Seasonal 40 spawning cycles of two California , Pleuronichthys verticalis () and Hippoglossina 30 stomata (). Bull. Mar. Sci. 32:347-350. ORANGE COUNTY 20 •Grier, H.J. 1981. Cellular organiza- 24 HOUR STUDY tion of the testis and spermatogen- esis in . Amer. Zool. NUMBER OFNUMBER TAXA 10 21:345-357 •Gruber, D., E.M. Ahlstrom, and 0 M.M. Mullin. 1982. Distribution of 0 10203040506070 ichthyoplankton in the Southern California Bight. Calif. Coop. NUMBER OF STOMACHS . Fish. Investig. Rep. 23:172-179

160 Table 2. Stomach contents of Pleuronichthys verticalis collected off Orange County in 1992. O=occurrence of prey in stomachs, N=number of prey, W=weight of prey, IRI=index of relative importance (modi- fied from Pinkas et al. 1971).

PREY ITEMS % 0 % N % W IRI

Bivalvia 2 9 6 4 4 6 3,190 Veneroida 2 3 5 7 4 1 2,229 Solenidae 2 3 5 7 4 1 2,229 Solen roseaceous 23 57 41 2,229 Gastropods 3 1 0 2 Polychaeta 148 8 8 160 36,694 Capitellida 1 0 4 6 Maldanidae 1 0 4 6 Asychis disparidentata 104 6 Eunicida 1 3 7 4 1 1 8 Onuphidae 1 3 7 4 118 Diopatra ornata 11 7 3 117 Diopatra sp. 1 0 0 1 Phyullodocida 1 0 1 1 Sigalionidae 1 0 1 1 Sthenelanella uniformis 101 1 Sabellida 1 6 8 7 1 6 4 Sabellidae 1 6 8 7 1 6 4 Chone veleronis 65776 Spionida 1 1 6 6 1 1 4 Spionidae 1 1 6 6 1 1 4 Paraprionospio pinnata 96487 Terebellida 1 3 9 3 2 5 2 1 Ampheritidae 3 3 1 1 0 Melinna oculata 33110 Teribellidae 1 0 6 3 1 3 7 6 Amaeana occidentalis 104 5 Pista alata 8 5 27 246 Pista sp. 1 0 0 1

•Luckinbill, L.S. 1969. Distribution 62. Office of Ocean Resources in the California Current region: and feeding relationships of the Conservation and Assessment, Taxa with 1000 or more total flatfishes Pleuronichthys verticalis Rockville, MD. 404 pp. larvae, 1951-1984. Calif. Coop. and Pleuronichthys ritteri. M.S. •Miller, D.J. and R.N. Lea. 1972. Ocean. Fish. Investig. Atlas No. Thesis, San Diego State Univer- Guide to the coastal marine fishes 31. 233 pp. sity. 81 pp. of California. Calif. Dept. Fish •Pinkas, L., M.S. Oliphant, and •Marquardt, D.W. 1963. An algo- Game, Fish Bull. 157. 249 pp. I.L.K. Iverson. 1971. Food habits rithm for least squares estimation •Morris, R.H., D.P. Abbot, and E.C. of the , bluefin, and of nonlinear parameters. J. Soc. Haderlie. 1980. Intertidal Inverte- in California waters. Calif. Indus. Appl. Math. 11:431-441. brates of California. Stanford Fish Game 152:1-105. •Mearns, A.J., M. Matta, G. University Press, Stanford, Califor- •Ross, J.L. and J.V. Merriner. 1983. Shigenaka, D. MacDonald, M. nia. 65 pp. Reproductive biology of the Buchman, H. Harris, J. Golas, and •Moser, H.G., R.L. Charter, P.E. blueline tilefish, Caulolatilus G. Lauenstein. 1991. Contaminant Smith, D.A. Ambrose, S.R. Char- microps off North Carolina and trends in the Southern California ter, C.A. Meyer, E.M. Sandknop, South Carolina. Fish. Bull. U.S. Bight: Inventory and assessment. and W. Watson. 1993. Distribu- 81:553-568. NOAA Tech. Mem. NOS ORCA tional atlas of fish larvae and eggs

161 • 162 Sumida, B.Y.,E.H.Ahlstrom,and verticalis Normalized meanstomachfullness(±S.E.)for Figure 10. 77:105-154. Pleuronectiformes). pigmented larvae(Pisces, eastern NorthPacificwithheavily ment ofsevenflatfishesthe H.G. Moser.1979.Earlydevelop-

NORMALIZED MEAN FULLNESS 0.0 0.2 0.4 0.6 0.8 1.0 collectedoffOrangeCounty.

500

700 Fish. Bull.U.S.

900 SUNRISE 1100

TIME OF DAY 1300 SUNSET

stomach contents. Cummings foridentifyingthe field; andD.TsukadaF. Diehl forhelpinthelaband during theproject;H.StubbsandD. Cross forsupportandguidance 1500 Author LarryCooperthanksJ. Acknowledgements 1700

1900 Pleuronichthys 2100

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