MARICULTURE PROGRAM 1983-84 The-mariculture staff is for from the very appreciative the support following: SID W. RICHARDSON FOUNDATION CAESAR KLEBERG FOUNDATION FOR WILDLIFE CONSERVATION GAME CONSERVATION INTERNATIONAL SPECIAL APPROPRIATION BY THE UNIVERSITY OF TEXAS BOARD OF REGENTS TEXAS SEA GRANT COLLEGE PROGRAM NATIONAL SCIENCE FOUNDATION INTRODUCTION THE MARICULTURE RESEARCH PROGRAM at The University of Texas, Port Aransas Lab has only been in existence for a few years but has already dealt with some of the most difficult aspects of finfish mariculture. Ours is a unique team approach to marine fish culture based on first determining the underlying biological processes which control reproduction, survival, to and growth, and secondly applying these facts to culture and eventually mass production. Thus the knowledge gained from basic research on the ecology, physiology and biochemistry of a species such as redfish will provide the technical background necessary for development of reliable techniques for culture. The is composed of a team of scientists program conducting research in the areas of maturation and spawning, reproductive and stress physiology, nutrition, physiological-ecology and bioenergetics and larvae, natural habitat evaluation and out. of eggs grow PERSONNEL Associ ate Di rector Research Technicians MSI Mariculture Program Wohlschlag, N. Arnold, C.R. Munoz, J. Research Scientists Graduate Students Holt, G.J. Gourley, J. Thomas, P. Juedes, M. Lee, W. Robertson, L. Smith, J. Post Doctoral Associate Trant, J. Wofford, W. Secretary Associates Pena, D. Research Holt, S. Brown, N. MARICULTURE REPORT 1983-84 The mariculture program of the Marine Science Institute has had another very productive year. We have published 29 scientific papers, two made 17 popular articles, presentations at national and international scientific meetings, and numerous presentations to civic clubs and other groups. At present, 5 graduate students and one post-doctoral fellow are being trained in our program. A new project was started this year to study the hard shell clams in Texas bays. This work is in collaboration with Dr. Tom Bright of Texas A&M University. Maturation and Spawnin The red drum which began spawning in August 1980 continued spawning until December 1983. At this time the extreme cold weather caused the water temperature in the fish tanks to drop to well below the spawning temperature for red drum; the temperature did not rise above 20°C until March 1984. Spawning ceased during this period, but resumed again in March when the water temperature again reached spawning temperature. These fish have continued to spawn since then, but the size and frequency of spawns has decreased to that observed before the onset of the cold water compared From August 1980 to December 1983 there were 253 spawns in temperatures. 41 months estimated 130 million eggs. producing an The red drum which were spawned and raised in the laboratory and first in April 1983 have continued to during the spawned spawn except water These fish have 95 times with period of cold temperatures. spawned the last November 9, 1984. Offspring from these fish are spawn occurring being reared for selective breeding studies. Eighteen red snapper have been selected for spawning studies. These fish were captured in the wild as juveniles and are now three years old. We are anticipating that these fish will begin spawning next May. Studies on Early Life Histor Lab studies on the early life history of fish are aimed toward defining optimal conditions for survival and growth of the eggs, larvae and juveniles. Fish growth and development result from complex interactions of external biotic and abiotic factors acting on the organism, and the internal state of that organism. Ambient temperature is an important regulator of growth and we have previously reported the effects of temperature on larval red drum growth and development. Our work has implicated other environmental and biotic factors which directly relate to growth rate. These include food, both type and size or amount, salinity, water quality and fish density. The last factor is particularly important because the most efficient fish culture methods demand high fish density in limited space. Results of our initial density studies indicate a strong negative correlation between growth rate and the number of fish. Two month old red drum growth rates were lowest at a density of 4 fish per liter and were highest at 0.5 fish per liter (Figure 1). Younger fish showed the same relationship, but growth rate was also affected by the size of the rearing container. The best growth occurred in the largest container at densities of less than 10 fish liter. From this work we concluded that per growth rates and fish density are negatively correlated, and that container size and density effects are interactive and confound the growth-rate density relationship. Further work will allow us to identify optimal conditions of density and container size for culturing all stages of red drum and to understand the biological processes underlying density Figure 1. Density dependent growth rate data for red drum grown for one L tanks. month in 10 lab and line) (solid collected field between drum. rates red growth line) of (dashed comparison reared A 2. Figure dependent growth rates. Another question we have asked is how do lab spawned and reared red drum compare to naturally occurring populations? Are our lab fish normal or are we producing an animal which is different in its growth and due lab conditions? development to To answer this question a collaborative study was initiated to compare lab and wild fish. Red drum larvae were collected with a plankton net near and in with Aransas Pass and a benthic marsh net in grass beds in Aransas Bay. The of these larvae determined age were by counting daily growth rings on the otoliths. We first verified this aging known fish technique using age grown in our greenhouse in 20 ft diameter fiberglass tanks. Red drum larvae ,could be successfully aged by these techniques up to about 15 days of age. Regression of standard length on age of the larvae showed very similar growth rates for lab reared (greenhouse) and wild caught red drum difference between the two (Figure 2). There was no significant growth rates. Larvae reared in smaller containers or in cooler conditions in the lab did not grow as quickly, however. Earlier we noted a general tendency for lab raised red drum of the same age to vary greatly in size and development. The formation of fins and scales was more closely related to the size of the fish than to age. this in the wild red drum that We investigated caught were aged using found similar variation in the wild fish. We were able otolith counts. We to predict the stage of development of the wild fish based on correctly that is of 64 wild fish examined showed the exact length; eighty percent same relationship of development to standard length as was seen in the lab and reared fish. These results show that our culture conditions spawned grow young fish comparable to the wild populations and give us the confidence to generalize results of lab experiments to natural red drum populati ons. 'During the last one and a half years we have conducted two fish egg sampling projects; one in the shallow near-shore waters of the Gulf of Mexico and the other in the Redfish Bay-Aransas Bay system. The purpose of these studies was to determine the spawning sites for red drum, spotted seatrout and other closely related sciaenid fish. Eggs of sciaenids, as well as many other marine fish, are released into the water and fertilized. The eggs are positively buoyant in sea water, so they float. Our sampling strategy was to take duplicate plankton tows at a selected site for preservation and a third sample for living eggs. In the lab the live eggs were sorted from the live sample. Sciaenid eggs are distinctive and could be sorted out from other eggs without much difficulty, but since all sciaenid eggs look alike we could only separate them by size (egg diameter). We then hatched the eggs and raised the larvae until we could positively identify them. During the spring we sampled for spotted seatrout eggs in an attempt Data from and to identify their spawning site. gill net trammel net males and females in collection made by co-workers showed that running ripe spawning conditions occurred at their collecting sites, and we wanted to there. verify that the fish were actually spawning We collected eggs, in conjunction with a 24-h sampling of the adults by co-workers in the mariculture program, by towing a plankton net near the dawn and noon. Data from the 24-hr sampling showed site at dusk, midnight, were taken in the evening near sunset and no primarily newly spawned eggs in the new eggs were collected later at night or morning. Developmental collected live at 2000 hours and reared in the lab stages of new eggs mirrored the stages of in each tow. eggs collected subsequent plankton To define the time spawning more precisely a series of duplicate samples were taken every 20 minutes from before dark until well after dark. Only well developed embryos were collected in the early samples. New eggs occur began to near sunset followed in time by later cel 1-division stages until 10:50 when pm the majority of the eggs were in late cleavage. Spawning occurred over a period of at least three hours but most spawning, evidenced by the frequency of a newly fertilized was limited to a one eggs, hour period beginning about one half hour after sunset (Figure 3). In three other series of samples taken from before dark to several hours after dark, greater than 50 percent of the new eggs were collected during the period one half hour before sunset to one and one half hours after sunset. Spawning data on silver perch was collected along with spotted seatrout because eggs of the two species co-occurred in most of the Silver of plankton samples. perch spawning occurred over a longer period time but the major pulse was over a period of a few hours after sunset. On several other dates from April through September samples taken during the daylight hours from 10:00 am to 8:00 pm contained spotted seatrout and silver perch eggs and all were in a predictable stage of embryo development based on spawning near sunset the previous day. information on several other sciaenids has been developed Spawning by back calculating from eggs in later stages of development collected the day following spawning. We have now gathered data on spawning times for seven species of sciaenids (Figure 4). Spawning in silver perch and spotted seatrout may extend from 1-1/2 hr before sunset to 2-1/2 hrs after, but the of the were in a relatively narrow time majority eggs spawned samples. plankton in eggs new of number on based seatrout spotted for time spawning Diel 3. Figure sunset. of time ss= period near sunset (shown by boxed areas on Figure 4). These are the only two species for which we have such precise data on spawning times. Spawning information for the other sciaenids probably represents peak spawning times for those species. Our data from lab spawning of red drum is also shown in the figure. Both direct and indirect evidence from our lab and field research indicates that dusk spawning is a general reproductive strategy for sciaenid Sunset is fishes. implicated as an environmental cue that may sciaenid Dusk trigger spawning. is a time when both light quantity and are exerts spectral quality changing swiftly, and a strong selective force on the behavioral adaptations of many animals. Sciaenids use sound for courtship, especially in the final stages. Visual cues are probably not important, so spawning at or near dark is no problem. Synchronous spawning is very important to insure fertilization of the numbers that released into the water column. But large of eggs are why is spawning confined to the evening? If light intensity, or the rate of change in light intensity is a factor timing the occurrence of spawning, then dawn could be a cue just as well as dusk. An advantage to dusk that the be in the dark and spawning may be planktonic eggs can dispersed thereby avoid a large group of predators from converging on the mass of newly spawned eggs. We suggest that mass spawning at dusk, involving large numbers of individuals, is an adaptation that reduces egg loss due to predation. This is based on three assumptions: (1) large number of eggs released by these fishes to individual in red drum) tend to potential (up 2,000,000 per swamp on and egg predators, (2) darkness reduces feeding eggs by pi anktivoces, (3) low egg density which results from overnight dispersal reduces spawning of bars) (open Sciaemds. _ of intensity species maximum seven and for bars) sunset (solid of time range to Estimated relative 4 Fiqure predation during the day. We have just begun to test these assumptions. One experiment entailed feeding red drum eggs to red drum larvae or juveniles under both light and dark conditions. Results of this experiment indicate that low density does reduce predation. In both treatments, and with both larvae and juvenile fish, none of the in low densities (1 10 4 1 eggs or eggs per found tank) were and eaten. In the high density test (100 eggs per tank) the small fish did not eat the eggs in darkness but ate 100% of the eggs in the light. The larger fish ate equal numbers of eggs in the light and dark at but high density. These results were ambiguous may indicate that size or trophic level of the fish is important in egg predations. The experiments will be repeated with species that occur in the water column that such are potential egg predators as bumpers, leather jackets, and small jack fish. Reproductive Physiology Research efforts have been divided between the collection of blood and gonadal samples from wild populations of spotted seatrout and the analysis of data collected during the past two years. We now have sufficient field samples to determine the entire seasonal and daily cycles of and steroid hormone fluctuations. The analysis of gonadal development blood and gonadal tissues is incomplete, but our preliminary results indicate that the reproductive physiology of spotted seatrout differs considerably from that of most other teleost species investigated to date. in seatrout Ovarian development spotted has been examined of histologically and by measurement egg size. Oocyte (egg) maturation commences in December but the ovary does not begin to enlarge until March when there is a burst of growth and the diameter of the developing oocytes increases 3*5 fold. This oocyte growth is largely due to the sequestering of vitellogenin (yolk protein) so that by the end of March the ovary contains a batch of fully grown oocytes containing large numbers of yolk globules. Blood levels of two ovarian hormones, estradiol and testosterone, also show a dramatic increase during this time (Figure 5) Circulating levels of the two hormones are low during the initial stages of ovarian maturation in January and February, possibly indicating that early phases of oocyte growth are independent of ovarian hormone control. However there is a marked rise in plasma estradiol and testosterone levels in females during March at time a when vitellogenin production commences, suggesting a role for estradiol and possibly testosterone in the regulation of vitellogenin synthesis. Oocyte development is asynchronous during the spawning season (April-September), with many different sizes and development stages of oocytes present in the ovary at the same time (Figure the the 6). Throughout reproductive season majority of the oocytes are either at the resting (40-70 pm) or early developing stage (71-120 pm), and only a small percentage of the oocytes are mature. Blood estradiol and testosterone concentrations remain elevated during this period, suggesting that vitellogenesis continues up to the end of the spawning season. Only the final maturation and hydration and fully developed eggs undergo are numbers of released during spawning. However, large maturing oocytes (120-312 pm) are still present in the ovary of a spawning fish (running able ripe. Fig. 6). This female will probably be to spawn again when becomes final another batch of oocytes fully developed. During oocyte maturation the yolk coalesces, several large oil droplets form in the and the nucleus moves to the edge of the oocyte where it center of the egg, and the swell to their breaks down. Hydration occurs oocytes 2.5 times Plasma estradiol and testosterone levels in seatrout during the period of ovarian development. Figure 5. female spotted Relative diameters Figure 6. frequency of oocyte from female spotted seatrout in three different developmental stages. original size prior to ovulation and spawning. Final oocyte maturation is a highly synchronized and rapid process in spotted seatrout which occurs in the afternoon a few hours before spawning is probably controlled by and both pituitary and ovarian hormones. It has been shown in several fish species that a pituitary hormone, gonadotropin, stimulates the ovary to switch from production of estradiol and testosterone to the synthesis of a maturational hormone, 17a hydroxy, 20f3 dihydroprogesterone. However, evidence is accumulating that 17ahydroxy, 20f3 dihydroprogesterone is not a major maturational hormone in spotted seatrout and that another steroid controls this A research hormone, presently unidentified, process. major emphasis during the coming year will be to elucidate the chemical structure of this novel maturational steroid. There appears to be a marked daily rhythm of plasma estradiol and levels at dawn than at testosterone, circulating generally being higher dusk The of these hormonal flucturations is (Fig. 7). significance daily in detail. It is that this presently being investigated thought daily cycle of blood hormone levels plays an important role in initiating and the of final maturation in the ovaries of synchronizing process oocyte spotted seatrout. Stress Physiolo Common fish culture and stocking practices such as confinement, variable of stress in crowding, handling and transportation cause a degree fish. Acute stress, if severe enough, can result in high mortality, whereas chronic stress is often associated with reduced growth and resistance to disease. Stress causes a rapid increase in the levels of two adrenal hormones, adrenaline and cortisol, which in turn cause secondary 17 Figure 7. Diurnal changes in plasma estradiol and testosterone levels in female spotted seatrout during the spawning season. metabolic disturbances such as a marked increase in blood levels. glucose In a series of experiments conducted over the past year both blood cortisol and glucose have been monitored in red drum exposed to a variety of stressful In procedures. one experiment, fish were captured from a holding tank, transferred to a small live box and held there for 30 min before returned being to the raceways. This prolonged transfer procedure caused profound plasma corticosteroid and hyperglycemic stress 30 min responses later (Fig. 8). Cortisol concentrations had increased BOX and glucose titers 6X control levels. The hyperglycemia persisted for 24 hrs, but cortisol concentrations had returned to control levels 3 hrs. by Rapid transfer in which fish were exposed to air for only 5 sec did not significantly elevate plasma cortisol or glucose concentrations. In contrast, 2 min exposure to air caused a marked hyperglycemic response. cortisol levels were unaltered. Thus, the of the Circulating magnitude changes in plasma cortisol and glucose concentrations in red drum appear to depend upon both the intensity and duration of the adverse stimulus. Pretreatment of fish with the anaesthetics MS-222 and quinaldine-sulfate completely blocked these plasma cortisol and glucose stress responses. We are currently examining the anaesthetic properties of a new experimental metomidate. Metomidate to be extremely effective as an drug, appears anaesthetic in fish and also in reducing the response to stress. We plan to whether metomidate can be used to tranquil ize red drum during test transportation and stocking. Transportation and stocking procedures appear be particularly to stressful to fish, often resulting in significant mortality. Pilot studies were conducted to determine the degree of stress induced in juvenile red drum by transportation procedures and to assess the efficacy of Figure 8. Plasma cortisol and glucose dynamics in red drum after capture and transfer to a small live box for 30 minutes. anaesthetics in reducing stress responses and the adverse effects of stress. The effects of transportation for 5.5 hr in seawater (35 %•) on cortisol plasma dynamics in red drum are shown in Figure 9. There was a marked increase in cortisol levels 1.5 h after the beginning of transportation which was not blocked by anaesthetization with MS-222. However, the corticosteroid stress was transient and plasma response cortisol had returned to of near resting levels by the end transportation. These results suggest that capture and transfer to hauling tanks may be more stressful to fish than the transportation procedure. Studies On the Harpacticoid, Tisbe carolinensis During the past year, an attempt has been made to find a local harpacticoid which could be cultured with ease in the laboratory and also offered to red drum larvae and postlarvae. Recent studied from both Japan Israel several and showed that species of Ti sbe and Tigriopus were potential food organisms for hatcheries; they have been tested with great success. Accordingly, Ti sbe caroli nensi $ was selected as the bioassay studies. The is such organism in our species commonly found among algae as Ulva, Enteromorpha, Codiurn and Pictyota in the littoral zone about 0.2 to 2 m depth along the Texas coast. During the initial experiment, Ti sbe were offered four different two algal cultures, including one pennate diatom, one green alga and blue- Feeding and reproduction of Ti sbe in these algae were then green algae. monitored to determine the algal species which would support the best of the harpacticoids. The results indicated that the population growth tested. Under the diatom was the best diet among the algae laboratory and the time condition, 30t salinity 24°C, generation from hatching to Figure 9. Plasma cortisol levels of red drum during seawater (32ppt) transport and recovery. During transport, the fish were either non-dosed or dosed with 5 rng/1 MS-222. gravid female is estimated to be 7-8 days, with interclutch interval of 4 to 4-1/2 days. The brood size with both and but changed age food, averaged 36-45 eggs. The newly hatched nauplii are small and range 60-85 pm. The size of nauplii is best suited for red drum larvae at the onset of their first feeding. Adult Tisbe are dimorphic in size, females tending to be than the larger male. On average, male length is about 50-60% of the female length (0.60-0.82 mm). Hence, adult Ti sbe are probably an appropriate diet for fish larvae at age 14-21 days. These data suggest that Tisbe could be one of the most promising for copepods mass culture, and is a subject that deserves further studies. The other part of the study dealt with the chemical composition and of the red drum and larvae. showed dry weight Eggs during development no in their size but decrease in their progressive changes displayed a gradual weight. When hatched, the larvae weighed 50-54% of the fertilized eggs (X = 38 pg), and egg cases were about 10 pg each (26%), suggesting a mean interval. weight loss of 20-24% during this developmental Red drum eggs and larvae have also been prepared for future determinations of their chemical components including C, H, N elements and the major biochemical components of lipid, carbohydrate and protein. The ratios of C/N or C/H among the different developmental stages will then be and discussed in relation to their energy status. compared Natural Habitat Studies Continuing research on the utilization of seagrass meadows as and other sciaenids has areas by red drum yielded numerous nursery these often still about intriguing results yet findings pose more question of the first the early life history of these fishes. Timing recruitment of young-of-the-year (yoy) red drum has been very consistent from year to A site in Harbor has been year, Island sampled weekly from August to 31 December for four years. The first yoy red drum have been taken between the 20th and the 25th of September each year. Most of these early recruits 9 10 are to mm standard and our length length-age regression formula, derived from last year's otolith aging indicates these fish studies, are about 21 days old. This indicates that the of spawning begins about Ist September. This annual consistency in recruitment indicates an equivalent consistency in the initiation of spawning each fall and suggests that spawning starts about the first week of September. Our laboratory work on has shown that a combination of shortening and spawning day length lowering water temperature can initiate spawning. In the oceans the changes in day length is a consistently reliable annual factor whereas water temperature is quite variable. Thus it appears that changing day length may be the key factor in initiating spawning in red drum. This is fertile ground for future research. Examining length-frequencies of these newly recruited red drum also provides an insight into the length of the spawning period. Table 1 shows that 7 and 8 mm fish were not taken after the second week in November. This would suggest that spawning had creased by the 2nd week of October and indicates there is a relatively short 4 to 5 week spawning period for red drum in south Texas. The maximum density of yoy red drum observed at our long term data site in Harbor Island for the 1983 spawning season was 7.7 fish per m 2. 2) and This is very the maximum densities observed in 1980 (7.8 m similar to 1981 (7.9 m 2) but well below the unusually high density of 35.2 m 2 observed 8 Dec 1 Island 22Nov 21 1 Harbor at 221 322211 16 Nov sled table. 8 1211 11 bottom Nov the in 4 33231121 2 in Nov 22 given caught 5133154321 1 is 1128 Oct drum length 426151 1 red 14 19 Oct of each 9652 11 2 of 14Oct 14 distribution 22312 individuals 10 Oct of 1 28 Sept number Length-frequency 1 the 23 Sept 1. 789 1011121314151617 181920 212223 Table Length (mm) in 1982. Our data analysis have not revealed any causal relationships between abiotic factors and the high recruitment of 1982 but the very base consistent densities of the other years may allow us to establish a line for "normal" recruitment so we can recognize and investigate unusually high or low recruitment periods. PUBLICATIONS Arnold, C.R. 1983. U.T.'s Marine Fish Research Program. Gulf Tide, Nov/Dec pp. 5-8. Arnold, C.R, 1984. Maturation and spawning of marine finfish. Technical Report Jm Carl J. Sindermann (ed.), Proc. of the 7th U.S.-Japan meeting on aquaculture, marine finfish culture, Tokyo, Japan,Oct. 3-4, 1978, p. 25-27. NOAA Tech. Rep. NMFS 10. Brown, N.J., P, Thomas and C.R, Arnold. 1983, Different life history of the strategies spotted seatrout, Cynoscion nebulosus, in a Texas and a Virginia estuary. Estuaries 6:260. (Abstr.) Carr, R.S., M.B. Bally, P. Thomas and J.M. Neff. 1983, Comparison of methods for determination of ascorbic acid in animal tissues. Anal. Chem. 55:1229-1232. Crocker, P.A., C.R. Arnold, J.A. Deßoer, and J. Holt. 1983. Blood osmolality shift in juvenile red drum (Sciaenops ocellatus Linnaeus) exposed to freshwater. J. Fish. Biology 23:315-319. Crocker, P.A., M, Gotto, J.A. Deßoer, G. Joan Holt, and C.R. Arnold. Notes on the surface structure of the gill arch epithelium in juvenile red drum, (Sciaenops ocellatus L.) exposed to salt and fresh water. Copeia (in press). Gomez-Sanchez, E.P., C.E. Gomez-Sanchez, J.S. Smith, M.W. Ferris, M. 1984. and of 18­ Foecking. Receptor binding biological activity hydroxycortisol. Endocrinology 115(2):462-466. Gomez-Sanchez, C.E., J.S. Smith, M.W. Ferris and E.P. Gomez-Sanchez. 1984. Renal receptor-binding activity of reduced metabolites of aldosterone: Evidence for a mineralocorticoid effect outside of the classic aldosterone receptor system. Endocrinology 115(2):712-715. Grier, H.J., J.S. Smith and C. Zahnow. 1984. Asynchronous annual reproductive cycles between the atheriniform teleosts Fundu!us grandis (Cyprinodontidae) and Poecilia 1 atipinna (Poeciliidae). Arnerican Zoologist 23(4):1022. (Abstr.T” Holt, G. Joan and C.R. Arnold. 1983. Effects of ammonia and nitrite on growth and survival of red drum eggs and larvae. Trans. Amer. Fish. Soc. 112(2B):314-318. Holt, G. Joan and K. Strawn. 1983. Community structure of macrozooplankton in Trinity and upper Galveston Bays. Estuaries 6:66-75. Holt, S.A., C.L. Kitting and C.R. Arnold. 1983. The distribution of young red drum (Sciaenops ocellatus) among different seagrass meadows. Trans. Amer. Fish. Soc. 112:267-271. Holt, G. Joan, Scott A. Holt and C.R. Arnold. 1983. Spawning synchrony in sciaenid fishes. Estuaries 6:261. (Abstr.) Holt, S.A. and G.J. Holt. 1983. Cold deaths of fishes at Port Aransas, 1982. Southwestern Naturalist 28:464-466. Texas, January Lee, W.Y. and C.R. Arnold 1983. Chronic toxicity of ocean-dumped valida. pharmaceutical wastes to the marine amphipod Amphithoe Mar. Pollut. Bull. 14(4):150-153. Holt and Arnold. 1984. Growth of red drum (Sciaenops Lee, W.Y., G.J. C.R. ocellatus) larvae in the laboratory. Trans. Amer. Fish. Soc. 113: 243-246/" Kamstra, G.K, P, Thomas and Janet Sadow. 1983, Evaluation of changes in the secretion of corticotrophin releasing activity using the isolated rat hypothalamus incubated in vitro. J. Endocrinol. 97: 291-300. Snyder, D.E, and G.J. Holt. 1984, ELH-AFS Terminology Workshop Report. Newsletter 5(2):14-15. Thomas, P., M.B. Bally and J.M. Neff, Influence of some environmental variables on the ascorbic acid status of mullet (Mugil cephalusLinn.) tissues. 11. Seasonal fluctuations and biosynthetic ability, (in press J. Fish Biology) P. Influence of Thomas, some environmental variables on the ascrobic acid status of mullet (Mugil cephalus Linn.) tissues. I. Effect of salinity, capture-stress and temperature. J. Fish. Biology (in press) Thomas, P. Biochemical of marine fish to responses pollutants, (chapter in press in CRC Handbook on Pollutant Studies in Marine Animals edited by C.S, Giam and L.E. Ray). Thomas, P. and H.W. Wofford. 1984, Elevated acid soluble content in fish hepatic tissue: a response to pollutants. Mar. Environ. Res 14: 486-488. Thomas, P, and H.W, Wofford, 1984. High-performance liquid chromatography of corticosteroids in vertebrate plasma: Assay of cortisol in mullet and corticosterone in the rat. Comp. Biochem. Physiol, 786:473-479. Thomas; P. and H.W. Wofford. 1984. Effects of metals and organic compounds on hepatic glutathione, cysteine and acid-soluble thiol levels in mullet (Mugil cephalus L.). Toxicol. Appl. Pharmacol. 76:172-182. Thomas, P. and J.M. Neff. 1984. Effects of a pollutant and other environmental variables on the ascorbic acid content of fish tissues. Mar. Environ. Res. 14:489-491. Thomas, P. and H.W. Wofford. 1984. Interactions of mercury with acid soluble thiols in the striped mullet (Mugil cephalus). Fed. Proc. 43, 337. (Abstr.) Thomas, P. and J.M. Neff. Plasma corticosteroid and glucose responses to pollutants in striped mullet: different effects of naphthalene, benzo[a]pyrene and cadmium exposure. In: Physiological Effects of Marine Pollutant Stress. Eds. A. Calabrese, F.P. Thurberg, F.J. Vernberg, and W.B. Vernberg. University of South Carolina Press, (in press) Vetter, R.D., R.E. Hodson and C. Arnold. 1983. Energy metabolism in a J. rapidly developing marine fish egg, (Sciaenops ocellata). Can. Fish. Aquat. Sci. 40(5):627-634. Wofford, H.W. and P. Thomas. 1984. Comparison of NADPH-dependent lipid in rats and fish. Fed. Proc. 43, 703. (Abstr.) peroxidation Wofford, H.W. and P. Thomas. 1984. Interactions of cadmium with sulfhydryl-containing compounds striped (Mugil cephalus in mullet L.). Mar. Environ. Res 14:119-137. PRESENTATIONS Arnold, C.R. 1984. Mariculture research at the University of Texas. of the Proceedings 1984 Fish Farming Conference and Annual Convention of the Fish Farmers of Texas 106-111. Brown, N.J., P. Thomas and C.R. Arnold, "Different life history strategies of the spotted seatrout, Cynoscion nebulosus, in a Texas and a Virginia estuary." 7th Biennial International Estuarine Research Conference, Virginia Beach, Virginia, October 22-26, 1983. Brown, N.J., P. Thomas and C.R, Arnold, "Reproductive biology of female spotted seatrout, Cynoscion nebulosus, in a south Texas embayment." 64th Annual Meeting American Society of Ichthyologists and Herptologists, Norman, Oklahoma, 29th July 3rd August 1984. - Gourley, J.E. and N.J, Brown. "Observations on diurnal and spatial habitat partitioning among fishes along the edge of a tropical Thaiassia testudinum meadow." 64th Annuel Meeting American Society of - 3rd Ichthyologists and Herptologists, Norman, Oklahoma, 29th July August 1984. Holt, G. Joan, "An overview of factors controlling growth and development in lab-cultured red drum." Fisheries and Science Lecture Series at The University of Alaska, Juneau, May 15, 1984. Holt, G. Joan, "Studies of the early life history of red drum and other sciaenids." Seminar at the University of Texas at Austin, Port Aransas Marine Laboratory, April 13, 1984. Holt, G. Joan and C.R. Arnold. "Factors associated with optimal growth in lab cultured red drum." Bth Annual Larval Fish Confierence and International Symposium on the Early Life History of Fishes, Vancouver, Canada, May 6-10, 1984. Holt, G. Joan and S. Holt. "Spawning synchrony in sciaenid fishes." 7th Biennial International Estuarine Research Conference, Virginia Beach, Virginia, October 23-26, 1983. and 6. Holt. in Holt, S. Joan "Crepuscular spawning sciaenid fishes." Bth Annual Larval Fish Conference and International Symposium on the Early Life History of Fishes, Vancouver, Canada, May 6-10, 1984. Robertson, L., P. Thomas and C.R. Arnold. "Effects of handling procedures on plasma cortisol and glucose levels in cultured red drum (Sciaenops ocellata)." 114th Annual Meeting American Fisheries Society, Ithaca, New York, August 12-16, 1984. Thomas, P. "Role of glutathione in fish tissues." University of Texas at Austin, Marine Science Institute, Port Aransas, Texas, March 1984 (semi nar). Thomas, P. steroidogenesis teleosts." University of "Gonadal in Texas at Austin, Institute of Reproductive Biology, April 17, 1984 (seminar. Thomas, P., N.J. Brown and C.R. Arnold. "Diurnal rhythms of circulating gonadal steroids in female spotted seatrout (Cynoscion nebulosus) during the spawning season." 114th Annual Meeting American Fisheries Society, Ithaca, New York, August 12-16, 1984, P. and H.W. Wofford. "Interactions of with acid soluble Thomas, mercury thiols in striped mullet (Mugil cephalus)." Annual Meeting Federation of American Societies for Experimental Biology, St. Louis, Missouri, April 1-4, 1984. Thomas, P. and J.M. 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