Effects of Salinity on Growth, Survival, and Selected Hematological Parameters of Juvenile Cobia Rachycentron canadum

JOURNALOFTHE WORLD AQUACULTURE SOCIETY

Vol. 34, No. 4 December, 2003

Effects of Salinity on Growth, Survival, and Selected Hematological Parameters of Juvenile Cobia

Rachycentron canadum MICHAEL R. DENSON, KEVIN R. STUART, AND THEODORE I. J. SMITH

Marine Resources Research Insiituie, South Carolina Department of Natural Resources. P.O. Box 12559, Charleston, South Carolina 29422 USA

CHARLES R. WEIRlCH AND AL SEGARS Waddell Mariculture Center, South Carolina Department of Naiural Resources,

P.O. Box 809, Bluffton, South Carolina 29910 USA

Absiract-Cobia Rachycentron canadum juveniles ( I 19.7 mm TL, weight 8.5 g) were reared for 10 wk at three salinity levels: 5 ppt, 15 ppt. and 30 ppt. Growth and survival were determined through biweekly sampling. Blood samples obtained at termination of the study were analyzed to determine hematocrit, blood osmolality, and total protein. Results indicated that the overall growth of fish was significantly affected by salinity. Mean ( 2 SE) total length (TL) and weight of fish reared at a salinity of 30 ppt were 201.7 2 2.6 mm and 47.6 2 1.9 g, respectively, followed by fish reared at 15 ppt (182.2 2 1.7 mm, 34.1 ? 1.6 g). and 5 ppt (168.3 rt_ 5.8 mm TL, 28.3 2 2.3 g). Dif- ferences in specific growth rates among treatments for the 10-wk period were also significant. No differences were detected in mean survival among fish reared at salinities of 5, 15, and 30 ppt (84, 94, and 94%, respectively). However, fish reared at salinity 5 ppt appeared to be in poor health as skin lesions, fin erosion, and discoloration were evident. Analysis of blood re- vealed that, while no differences existed among treatments with respect to plasma total protein, fish reared at a salinity of 5 ppt exhibited significantly reduced hematocrit (25% vs. > 30%) and plasma osmolality values (318 vs. > 353 mmolkg) relative to fish reared at higher salinities. Cobia can tolerate exposure to low salinity environments for short periods of time without mortality; however, moderate to high salinities are re- quired for sustained growth and health of this species.

Cobia Rachycentron canadum occur in coastal waters of South Carolina from April-June as part of a seasonal spawning migration (Bearden 1961). This species is especially desirable because of its large size and excellent quality flesh. Although only seasonally available, this species is targeted locally by recreational fishermen. Occasion- ally, commercial fisheries harvest cobia as by-catch; however it is not a targeted spe-

cies and has acquired only limited regional exposure as a food fish (Shaffer and Nak- amura 1989; Brown-Peterson et al. 2001). Nonetheless, a premium market price for cobia steaks and fillets of $8.00/kg exists although supply is often limited and tem- porary (Rickards 2001).

Cobia exhibit extremely fast growth rates which make them attractive as a potential aquaculture species, reaching weights of 6- 8 kg during the first year of growth (Franks et al. 1999; Oesterling 2001; Chen et al. 2001; Chou et al. 2001). The majority of research on cobia has evaluated natural distribution of wild fish (Ditty and Shaw 1992; Franks et al. 1999; Hendon and Franks 2000), reproductive biology (Smith 1995; Franks et al. 1996; Brown-Peterson et al. 2001), and recreational fisheries (Richards 1967; Manooch and Laws 1979; Jones 1985). Joseph et al. (1964) began culture studies with cobia in the United States in 1964 in the Chesapeake Bay area. More re- cently, researchers have collected wild broodstock and manipulated photoperiod and temperature to condition fish to spawn with and without hormone treatment of fe- males (Caylor et al. 1994; Dupaul et al. 1997; Oesterling 2001). Caylor et al. (1994) have also explored the application and util- ity of sperm cryopreservation and its role in aquaculture of this species. Throughout the 199Os, the Taiwanese have experiment- ed with spawning of captured broodstock in ponds and have in the last several years de-

0 Copyright by the World Aquaculture Society 2003

496

SALINITY EFFECTS ON COBIA 497

veloped an extensive net pen culture industry (Su et al. 2000).

With significant efforts underway with respect to controlled spawning and larval production, the next logical step is to determine environmental requirements of this species to identify culture opportunities and maximize production. In the United States, shore-based production facilities are often economically inhibited by the high cost of coastal sites for extensive seawater pond systems or intensive seawater production facilities. The U.S. aquaculture industry is extremely interested in the identification of species with fast growth rates and high market value that may be adapted to freshwater or brackish water culture systems as is the case with the euryhaline hybrid striped bass Morone suxutilis X M. chrysops (Smith et al. 1986; Smith and Jenkins 1996). How- ever, little is known about the effect of salinity on growth and survival of larval and juvenile cobia. In addition, limited infor- mation exists with respect to the affects of salinity on physiology of this species. Of the suite of hematological parameters available to researchers assessing environmental affects on the physiological status of finfish, three are routinely measured: total protein, hematocrit, and osmolality. Total protein is a useful indicator of water balance and nu- tritional status (Tietz 1976) and is sensitive to environmental salinity (Verdegem et al. 1997; Chang and Hur 1999). Hematocrit, considered to be a useful indicator of anemia and overall health status of fish (Schreck and Moyle 1990), has been shown to be affected by environmental salinity (Leray et al. 1981; Peterson 1988). Osmo- lality has been shown to be an excellent physiological indicator of fish health status (Wedemeyer 1996) and is especially rele- vant with respect to assaying effects due to salinity (Hwang et al. 1989; Walker et al. 1989; Weirich and Tomasso 1991; Weirich et al. 1992; Altinok et al. 1998; LeBreton and Beamish 1998).

The South Carolina Department of Nat- ural Resources (SCDNR) initiated research

in 2001 as part of a national aquaculture research initiative to investigate cobia spawning, pond production methods, and environmental requirements. The study reported herein was designed to determine the effect of salinity on growth, survival, and selected hematological parameters of juvenile cobia.

Materials and Methods Juvenile cobia (90-d-old) were harvested

from tanks that were held at 33 ppt and 23 C at the SCDNR’s Waddell Mariculture Center (WMC) in Bluffton, South Carolina, USA and transported to the Marine Re- sources Research Institute (MRRI) in Charleston, South Carolina, USA on 22 July 2001. Fish were held for approximately 30 d in indoor tank systems maintained at 30 ppt salinity and 23 C before introduc- tion to the study. The 120-d-old cobia were randomly assigned to three treatment salinities (5, 15, 30 ppt) with acclimation to salinities of 5 and 15 ppt during a 60-min dilution from 30 ppt by adding dechlori- nated tap water.

The study began on 9 August 2001 with 300 fish (mean total length 119.7 mm and mean weight 8.5 g) divided equally into 12 circular tanks (1.98 m2 diameter X 0.8 m deep). Each treatment was replicated in four tanks containing 25 fish each. Each treatment group of tanks used recirculating seawater that had been chlorinated (for elimi- nation of potential pathogens) and dechlo- rinated. The 5-ppt water was pumped from a deep well and passed through an aeration/ degassing column. The column also provided denitrification prior to entering the lab- oratory. A mixture of 30-ppt seawater and 5-ppt well water provided the 15-ppt treatment water. Each treatment was connected to a separate system consisting of an 80-W UV filter (Aqua Ultra Violet, Temecula, California, USA), washed bead filter (Aquacenter, Inc. Leland, Mississippi, USA), and protein fractionation column.

Water quality analysis was conducted weekly. With the exception of salinity, no

498 DENSON ET AL.

differences were detected between treatments. Temperature and dissolved oxygen were measured with a YSI model 57 meter (Yellow Springs Instruments Inc., Yellow Springs, Ohio, USA). Mean values (ranges in parentheses) were 23.9 C (23.0-25.0 C) and 7.8 ppm (6.5-8.2 ppm), respectively. Total ammonia-nitrogen and pH were measured using Lamotte Octet Comparator test kit Models p5 I00 and PAN, respectively (Lamotte Chemical Co. Chestertown, Maryland, USA). Mean values (ranges in parentheses) for total ammonia-nitrate and pH were 1.0 ppm (0.0-1.0 ppm) and 7.9 (7.5-8.0), respectively. Salinity was moni- tored with a calibrated refractometer (Spar- tan Refractometers, Japan). After weekly water quality analysis was conducted, water was added to adjust for evaporative loss and to maintain salinity levels within 1 ppt of nominal treatment concentrations. Water samples obtained from the deep well in addition to samples of full strength seawater were also analyzed with a Perkin-Elmer Plasma 40 Emission Spectrometer (PerkinElmer Inc., Wellesley, Massachu- setts, USA) to test for metals and DX-100 Ion Chromatograph (Dionex Corp., Sun- nyvale, California, USA) to measure ion concentrations. Ions and metals measured in the 5-ppt well water were more variable than those of seawater. Total alkalinity (as CaCO,), calcium, and magnesium of well water were 210, 41, and 26 ppm, respectively, as compared to 232, 299, and 272 ppm, respectively, for the seawater.

Every 2 wk 10 cobia were randomly sampled from each tank to determine change in growth and the entire population was counted to determine survival. Sam- pled fish were anesthetized with quinaldine (0.05 ml/L). Feed level was adjusted based on sample weights for each tank. In the first month, fish were fed at a rate of 10.0% body weight/d (bw/d) thereafter fish re- ceived 7.5% bwld. All fish were fed a 0.3- cm diameter floating pelleted diet containing 44% protein and 20% lipid (Bums Mill and Feed, Inc., Franklinton, Louisiana,

USA). Feed quantity was based on total number of fish, and biweekly allocations were changed based on survival and growth (i.e., number of fishhank X (% bwld feed). Feed was distributed to fish using a Zeigler 12-h mechanical belt feeder (Zeigler Bros. Inc., Gardeners, Pennsylvania, USA). Mean specific growth rates (SGR) for the 10-wk period were calculated using the equation described by Benetti et al. (1995): SGR = (In W2 - In Wl)/t X 100, where W2 = final weight; WI = initial weight; t = time in d).

At termination of the study, five fish were randomly removed from each tank (N = 20/ treatment) to determine hematological parameters (hematocrit, plasma total protein, and plasma osmolality). Five individual measurements of each parameter were obtained from each sample and a mean calculated. Blood samples (1-2 mL) were ex- tracted from the heart using a syringe (3- mL capacity, 22-gauge needle; Becton Dickinson and Co., Franklin Lakes, New Jersey, USA). Each syringe was used only once. Before blood was obtained, needles were lightly coated with Na+-heparin. A small amount of whole blood from each sample was immediately transferred to Fisherbrandm heparinized (Na+-heparin) capillary tubes (Fisher Scientific, Pitts- burgh, Pennsylvania, USA); the remainder of the sample was transferred to a heparinized (Na+-heparin) collection tube (Vacu- t a ine9 , Becton Dickinson and Co.). Cap- illary tubes were centrifuged for 5 min at 7,200 rpm using a Clay Adam@ READA- C R I P centrifuge (Becton, Dickinson and Co.). Hematocrit (expressed as percentage of whole blood volume) was determined by measuring the length of packed cells using a hematocrit table. Whole blood samples contained in Vacutainee tubes were centrifuged for 5 min at 4,500 rpm using an International Clinical Centrifuge model 44670M-4 (International Equipment, Needham Heights, Massachusetts, USA). One drop of plasma from each tube was transferred to a Westover RHC-200ATC


handheld refractometer (Westover Scientif- ic, Inc., Woodinville, Washington, USA) for the determination of plasma total protein (expressed as g/dL). Plasma osmolality (expressed as mmol/kg) was determined by analysis of 10-pL samples using a Wescor Model 5 1 OOC vapor pressure osmometer (Wescor, Inc., Logan, Utah, USA).

Data on growth, survival, and hematological parameters were analyzed by ANOVA and Kruskal-Wallis one-way analysis of var- iance on ranks, as appropriate. Differences between treatments were determined using Tukey’s all pairwise multiple comparison tests and the Dunn’s method all pairwise multiple comparison tests (Sigmastat, Jandel Corporation, San Rafael, California, USA).

Results Results from the first sampling period

(week 2) indicated that significant differences existed with respect to mean total length (TL) and weight of fish reared at a salinity of 5 ppt compared to fish reared at salinities of 15 and 30 ppt (N = 4, df = 2,

P = 0.001) (Table 1). After the second sampling period (week 4) significant differences were detected between TL‘s of fish reared at each salinity level (N = 4, df = 2, P = 0.001). Fish reared at a salinity of 5 ppt weighed significantly less than fish reared at salinities of 15 and 30 ppt; however no differences in weight were detected between fish reared at salinities of 15 and 30 ppt (H = 9.269, N = 4, df = 2, P = <0.001) (Table 1). This pattern was also observed at week 6. At weeks 8 and 10, fish reared in each treatment were significantly different with respect to length and weight (Table 1).

Initially, fish reared at a salinity of 30 ppt appeared to be the most aggressive feeders, whereas fish reared at a salinity of 5 ppt were comparatively lethargic. Overall, fish reared at a salinity of 30 ppt exhibited length and weight increases (means ? SE) of 2.6 5 0.1 m d d and 0.8 2 0.1 g/d, respectively. This rate of growth was significantly (N = 4, df = 2, P = 0.001) greater than that of fish reared at 15 ppt (1.7 2 0.2

TABLE I . Totul Iength and weight (means 2 SE) of cobiu reared ut various salinities for 10 wk. Mean total length and weight ( 2 SD) at stocking was 119.7 2 11.3 and 8.5 2 2.8, respectively. Specific growth rate (SGR) ($,fish are expressed us the % body weight per day over the 10-wk study period. Values across columns not sharing the same letter are signijcant1.v different (P < 0.05).

Salinity (ppt)

Week 5 15 30

2 Length (mm) 135.1 ? 3.7 a 149.9 2 2.2 b 155.9 t 2.0 b Weight (g) 8.5 C 1.3 a 13.5 C 0.8 b 20.0 t 1.2 b

4 Length (mm) 150.2 C 3.1 a 161.4 t 2.6 b 172.9 ? 2.7 c Weight (g) 17.3 C 1 . 1 a 22.1 C 1.4 b 30.3 2 1.2 c

6 Length (mm) 154.0 C 2.3 a 165.2 ? 4.5 b 184.7 2 1.2 b Weight (g) 20.2 C 0.6 a 26.2 ? 2.3 ah 37.9 C 1.0 b

8 Length (mm) 164.7 C 3.1 a 181.5 2 4.7 b 196.4 ? 2.3 c Weight (g) 23.0 C 1.3 a 32.4 t 2.4 b 44.3 ? 0.6 c

10

Length (mm) 168.3 t 5.8 a 182.2 ? 1.7 b 201.7 2 2.6 c Weight (g) 28.3 2 2.3 a 34.1 C 1.6 b 47.6 _f 1.9 c SGR (% bw/d) 0.51 a 1.98 b 2.46 c

500 DENSQN ET AL

\ D O ,

8 2 ’ I

2 4 6 8 10

Weeks

FIGURE 1. Survival of cobia Rachycentron canadum juveniles ( 1 1 9.7 mm TL, weight 8.5 g) reared f o r 10 wk at three salinity levels: 5 ppi, 15 ppt, and 30 ppi.

mm/d, 0.4 2 0.1 g/d) and 5 ppt (1.1 2 0.3 mm/d, 0.2 ? 0.1 g/d). Mean overall SGR for the 10-wk study indicated that fish reared at a salinity of 30 ppt grew significantly faster at a rate of 2.46% bw/d whereas fish reared at salinities of 15 and 5 ppt grew at rates of 1.98 and 0.51% bw/d, respectively (Table 1).

At week 2 no mortalities were recorded suggesting that fish successfully acclimated to the treatment salinities. During weeks 3 and 4, several mortalities were recorded at salinities of 5 and 15 ppt. At week 6, survival of fish reared at a salinity of 5 ppt was 88% and the mortality rate for the remainder for the study declined. Many of the fish sampled from the 5-ppt treatment had eroded fins, ulcerations of the skin, and were emaciated. No mortalities were recorded until week 7 for fish reared at a salinity of 30 ppt. Mean survival of fish reared at both 15 and 30 ppt was 94% on week 10 (Fig. 1). However, no statistical

differences in survival were detected among treatments (H = 2.851, 2 df, P = 0.277) (Fig. 1).

Some differences in hematological parameters were detected among fish reared in the different salinities (Table 2). Mean hematocrit values of fish reared in the lower salinity treatment was 25.0% and was significantly lower than in the higher salinity levels which ranged from 30.0 to 32.0%. There were no differences among treatments in total protein values, which ranged from 2.5 to 3.1 g/dL (Table 2). Mean plasma osmolality increased with salinity and ranged from 3 18.1 to 355.4 mmol/kg (Table 2). While plasma osmolality of fish reared at 5 ppt was lower (P < 0.05) than that of fish reared at 30 ppt, no significant differences with respect to this parameter existed between fish reared at salinities of 5 and 15 ppt, or between 15 and 30 ppt (Table 2).

Discussion Juvenile cobia reared at a salinity of 30

ppt for 10 wk exhibited impressive growth, almost doubling in length and increasing in weight by a factor of 8. Results indicate that fish reared at 5 ppt initially grew well, but after 6 wk growth declined and mortalities began to occur. Although fish reared at a salinity of 5 ppt consumed their daily feed ration, an assortment of potentially stress- induced symptoms began to appear including lesions, fin erosion, and non-typical coloration. Many fish reared at this salinity also began to display a gray coloration in contrast to fish at the two higher salinities, which exhibited a typical color pattern consisting of blackhrown and white stripes.

TABLE 2. Hemaiologicul parameiers (means _C SE) of juvenile cobia reared at differeni salinities measured at termination of 10-wk growih irial. Values across columns not sharing the same letter are signifcanily differen f (P <0.05).

Salinity (ppt)

Parameter 5 15 30 ~

Hematocrit (%) 25.0 ? 1.3 a 32.0 ? 1.3 b 30.0 2 0.8 b Plasma total protein (g/dL) 2.5 ? 0.2 a 3.1 % 0.2 a 3.0 2 0.1 a Plasma osmolality (mmolkg) 318.1 ? 14.6 a 353.7 2 1.2 ah 355.4 ? 2.3 b

SALINITY EFFECTS ON COBIA 50 1

Plasma total protein levels did not differ among treatment groups, and fish were within the normal range reported for other teleosts (Wedemeyer 1996). However, hematocrit and plasma osmolality of fish reared at a salinity of 5 ppt were significantly reduced compared to values of fish reared at 15 and 30 ppt, respectively. In several freshwater teleosts, hematocrit has declined when fish were exposed to hypersaline environments (Leray et al. 198 1 ; Pe- terson 1988; Susanto and Peterson 1996). In this study it appears that hematocrit levels were reduced via exposure to hyposaline environments. However, reduced hematocrit of cobia juveniles reared at 5 ppt in the present study may have simply been the re- sult of disease or stress-induced anemia (Blaxhall 1972; Schreck and Moyle 1990). Stenohaline freshwater and marine teleosts are limited in their ability to osmoregulate over a wide range of salinities (Wedemeyer 1972, 1996). It is possible that an environmental salinity of 5 ppt is below the level that juvenile cobia can tolerate with respect to maintenance of ion and water levels. We should also point out that although a de- tailed chemical analysis was performed on the well water (5 ppt), there may indeed be additional components that were not measured in the analysis that may impact ion balance and inadvertently confound the treatment effect. It is also possible that stress associated with netting and handling during sampling may have induced osmo- regulatory dysfunction among fish in the lower salinity. This has been shown to occur in several species including red drum Sciaenops ocellatus (Weirich and Tomasso 1991) and white bass X striped bass Mo- rone chrysops X M. saxatilis hybrids (Weir- ich et al. 1992). Results suggest juvenile cobia reared at a salinity of 15 ppt can effec- tively maintain hematocrit and osmolality within ranges reported normal for teleosts; thus culture of this species at somewhat reduced salinities may be possible albeit with significantly slower growth.

Although the optimal temperature for

growth of cobia has not yet been determined, based on preliminary research cou- pled with anecdotal observations, it appears that growth is best at water temperatures ranging from approximately 2 6 3 0 C. For example, in Taiwan, cobia cultured in net pens are typically reared at temperatures within this range (Su et al. 2000). In a re- cent study, Weirich et al. (unpublished) reported SGR values for pond-reared juvenile cobia fed the same feeds as used in the present study at 35 ppt to be as high as 7.3% bwld at a mean water temperature of 28.9 C. In the present study although ambient mean temperature of all three treatments was 23.9 C, SGR values observed for cobia reared at salinities of 15 and 30 ppt (1.98 and 2.46% bwld, respectively) were com- parable to that of other marine finfish species including snook Centropomus undeci- malis (SGR = 2.08) and barramundi Lutes calcarifer (SGR = 2.49), and exceeded that reported for red drum S. ocellatus (SGR = 1.69) (Tucker 1989).

When not feeding, cobia typically rested on the bottom of the tank. Wild broodstock held at our facility also have been observed to display this behavior at lower temperatures but appear to be much more active when temperatures are greater than 27 C. It is probable that at closer to optimal rearing temperatures fish reared at I5 ppt would exhibit increased SGR values, perhaps closer to dolphin Coryphaena hippurus, long considered as having one of the fastest growth rates in teleost fish, with SGR values of 4.33% bwld (Benetti et al. 1995), 4.64% (Ostrowski et al. 1989) and as high as 13% bwld (Iwai et al. 1992).

As survival was not affected at a salinity of 15 ppt, production in brackish water systems (i.e., 50% seawater) may be possible. It is important that the minimum seawater concentration for adequate growth and survival be determined so that the economic balance between acceptable growth and facility location can be determined. Tucker ( 1988) found relationships between temperature and salinity in the culture of snook.

502 DENSON ET AL.

He showed that snook juveniles had higher specific growth rates at higher temperatures and that a balance in optimum temperatures with optimum salinities could be reached to yield equivalent growth rates.

Some of our preliminary studies with cobia involved non-acclimated exposure of animals to freshwater (0 ppt) (Denson unpublished). It was observed that fish sur- vived for several hours following such a treatment. Fish were also exposed to freshwater for a 30-min period and then returned to full strength seawater. These fish began feeding within an hour. Brief exposure to freshwater can be used therapeutically for parasite removal, especially for pathogenic parasites such as Amyloodinium sp., which has been responsible for numerous marine fish kills at facilities that use recirculating seawater systems (Lawler 1977a, 1977b; Paperna 1984; Ostrowski 2000). Our observations regarding the high level of tolerance of cobia to such treatment regimes suggest that these procedures could be incorporated in culture of this species.

In summary, findings suggest that cobia may be reared at least during part of their life cycle in intermediate salinities. High tolerance to euryhaline conditions for short periods of times also provides flexibility in disease treatment options for this species.

Acknowledgments

We thank Charles Bridgham and Louis Heyward for their assistance in monitoring and sampling the animals and Myra Brou- wer and Wallace Jenkins for reviewing this manuscript. This research was supported in part by the National Sea Grant College Pro- gram, under the National Marine Aquacul- ture Initiative (grant number NA 16RG 1646). This is contribution number XXX from the South Carolina Marine Resources Center.

Literature Cited

Altinok, I., S. M. Galli, and F. A. Chapman. 1998. Ionic and osmotic regulation capabilities of juvenile Gulf of Mexico sturgeon. Acipenser oxyrin-

chus. Comparative Biochemistry and Physiology I20A:609-6 16.

Bearden, C. M. 1961. Common marine fishes of South Carolina. Bears Bluff Laboratories, Wad- malow Island, SC.

Benetti, D. D., E. S. Iversen, and A. C. Ostrowski. 1995. Growth rates of captive dolphin, Coryphae- nu hippurus. in Hawaii. Fishery Bulletin 93: 152- 157.

Blaxhall, P. C. 1972. The hematological assessment of the health of freshwater fish. Journal of Fish Biology 4:593-604.

Brown-Peterson, N. J., R. M. Overstreet, J. M. Lotz, J. S. Franks, and K. M. Burns. 2001. Re- productive biology of cobia, Rachycentron canadum, from coastal waters of the southern United States. Fishery Bulletin 99( 1): 15-28.

Caylor, R. E., P. M. Biesiot, and J. S. Franks. 1994. Culture of cobia (Rachycentron canadurn): cryopreservation of sperm and induced spawning. Aquaculture 125:81-92.

Chang, Y. J. and J. W. Hur. 1999. Physiological re- sponses of grey mullet, Mugil cephalus and Nile tilapia Oreochromis niloficus by rapid changes in salinity of rearing water. Journal of Korean Fish- eries Society 32(3):3 10-3 16.

Chen, Y. -H., M. -S. Su, and I. C. Liao. 2001. Chal- lenges and strategies of cage aquaculture development in Taiwan. Book of Abstracts, Aquacul- ture 2001. World Aquaculture Society, Baton Rouge, Louisiana, USA.

Chou, R.-L., M.-S Su, and H.-Y Chen. 2001. Opti- mal dietary protein and lipid levels for juvenile cobia Rachycenrron canadurn. Aquaculture 193:

Ditty, J. G. and R. F. Shaw. 1992. Larval development, distribution, and ecology of cobia Rachy- centron canadurn (family: Rachycentridae) in the northern Gulf of Mexico. Fishery Bulletin 90(4):

Dupaul, W. D., M. J. Oesterling, and L. A. Rose. 1997. Marine finfish aquaculture in Virginia. Spe- cies profile: cobia (Rach-ycenrron canadurn). Vir- ginia Marine Research Report No. 97-4. Virginia Institute of Marine Science, College of William and Mary, Gloucester Point, Virginia, USA.

Franks, J. S., N. M. Garber, and J. R. Warren. 1996. Stomach contents of juvenile cobia, Rachy- centron canadurn, from the northern Gulf of Mex- ico. Fishery Bulletin 94:374-380.

Franks, J. S., J. R. Warren, and M. V. Buchanan. 1999. Age and growth of cobia, Rachycentron canadurn, from the northeastern Gulf of Mexico. Fishery Bulletin 97:459-47 I .

Hendon, J. R. and J. S. Franks. 2000. Seasonal move- ments and migratory patterns of cobia, Rachycen- tron canadurn. Annual report to U.S. Fish and Wildlife Service, Atlanta, Georgia. USA, and Mis-

8 1-89.

668-677.


sissippi Department of Marine Research. Biloxi, Mississippi, USA. Proj. No. F-120, Seg. No. 2.

Hwang, P. P., C. M. Sun, and S. M. Wu. 1989. Changes of plasma osmolality, chloride concentration and gill Na-K-ATPase activity in tilapia, Oreochromis mo.s.samhicu.s during seawater acclimation. Marine Biology 100:295-299.

Iwai, T., Jr., H. Ako, and L. E. Yasukochi. 1992. Use of beef liver in the diet of juvenile mahi-mahi, Coryphuena hippurus L. World Aquaculture

Jones, A. C. 1985. Ocean habitat and fishery resources in Florida. Pages 437-543 in W. Seaman, Jr., editor. Florida Aquatic Habitat and Fishery Resourc- es. Florida Chapter of the American Fisheries So- ciety, Kissimmee, Florida, USA.

Joseph, E. B., J. J. Norcross, and W. H. Massmann. 1964. Spawning of the cobia. Rachycenrron cnn- udum. in the Chesapeake area, with observations of juvenile specimens. Chesapeake Science 5:67- 71.

Lawler, A. R. 1977a. The parasitic dinoflagellate Amyloodinium ocellurum in marine aquaria. Drum and Croaker 17(2): 17-20,

Lawler, A. R. 1977b. Dinoflagellate (Arnyloodinium) infestation in pompano. Pages 257-264 in C. J. Sinderman, editor. Disease diagnosis and control in North American aquaculture. Elsevier Scientific Publishing Co., New York, USA.

LeBreton, G. T. 0. and F. W. H. Beamish. 1998. The influence of salinity on ionic concentration and osmolarity of blood serum in lake sturgeon. Acipenser fulvescens. Environmental Biology of Fishes 52~477-482.

Leray, C., D. A. Colin, and A. Florentz. 1981. Time course of osmotic adaptation and gill energetics of rainbow trout, Salmo gairdneri following abrupt changes in external salinity. Journal of Comparative Physiology 144: 175-1 8 1.

Manooch, C. S. 111 and S. T. Laws. 1979. Survey of the charter boat troll fishery in North Carolina, 1977. Marine Fisheries Review 41: 15-27,

Oesterling, M. 2001. Cultured cobia satisfy taste buds. Virginia Marine Resource Bulletin 33(2). Virginia Sea Grant Communications, Virginia Institute of Marine Science, Gloucester Point, Virginia, USA.

Ostrowski, A. C., C. Brownell, and E. 0. Duerr. 1989. Growth and feeding rates of juvenile dol- phins (Coryphuenu hippurus) fed a practical diet through growout. World Aquaculture 20(4): 104- 105.

Ostrowski, A. C. 2000. Dolphin (mahi-mahi) culture. Pages 232-239 in R. R. Stickney, editor. Encyclo- pedia of aquaculture. Wiley and Sons. New York, USA.

Paperna, 1. 1984. Reproduction cycle and tolerance to temperature and salinity of Amyloodinirtm ocel-

23(3):49-5 1.

larum (Brown 193 I ) Dinoflagellida. Annuals of Parasitology 59:7-30.

Peterson, M. S. 1988. Comparative physiological ecology of centrarchids in hyposaline environments. Canadian Journal of Fisheries and Aquatic Sciences 45327-833.

Richards, C. E. 1967. Age, growth, and fecundity of the cobia, Rachycentron canadum, from Chesa- peake Bay and adjacent mid-Atlantic waters. Transactions of the American Fisheries Society 96( 3):343-350.

Rickards, W. L. 2001. Sustainable cobia culture and fisheries. Virginia Sea Grant Publication VSG-OI- 07. Virginia Sea Grant, Charlottesville. Virginia, USA.

Shaffer, R. V. and E. L. Nakamura. 1989. Synopsis of biological data on the cobia Rachycenrron cun- aduni (Pisces: Rachycentridae). FA0 Fisheries Synopsis 153 (NMFSIS 153). USDOC NOAA Technical Report NMFS 82. US Department of Commerce, Washington, D.C., USA.

Schreck, C. B. and P. B. Moyle, editors. 1990. Meth- ods for fish biology. American Fisheries Society, Bethesda, Maryland, USA.

Smith, J. W. 1995. Life history of Cobia Rach.ycm- rron canadum (Osteichthyes: Rachycentridae) in North Carolina waters. Brimleyana 23: 1-23.

Smith, T. I. J. and W. E. Jenkins. 1996. Regional development of hybrid striped bass aquaculture in the southeastern U.S. Pages 175-179 in T. G. Heggbergett, editor. The role of aquaculture in world fisheries, theme 6. Proceedings of the World Fisheries Congress, Oxford and IBH Publishing, New Delhi, India.

Smith, T. I. J., W. E. Jenkins, and R. W. Haggerty. 1986. Growth and survival ofjuvenile striped bass (Morone saxatilis) X white bass (M. chrysops) hybrids reared at different salinities. Proceedings of the Annual Conference of Southeastern Associa- tion of Fish and Wildlife Agencies 40:143-151.

Su, M.-S., Y.-H. Chen, and 1. C. Liao. 2000. Poten- tial of marine cage aquaculture in Taiwan. Pages 89-98 in 1. C. Liao and C. K. Lin, editors. Pro- ceedings of the First International Symposium on Cage Aquaculture in Asia. Taiwan Fisheries Re- search Institute, Keelung, Taiwan.

Susanto, G. N. and M. S. Peterson. 1996. Survival, osmoregulation, and oxygen consumption of YOY coastal largemouth bass, Microprerus salnioides exposed to saline media. Hydrobiologia 323:119- 127.

Tietz, N. W. 1976. Fundamentals of clinical chemis- try. W. B. Saunders, London, England.

Tucker, J. W., Jr. 1988. Growth of juvenile spotted sea trout on dry feeds. The Progressive Fish Cul- turist 50:39-4 l .

Tucker, J. W., Jr. 1989. Development of feeds for

504 DENSON ET AL.

marine and brackish water fish. World Aquacul- ture 20: 106.

Verdegem, M. C. J., A. D. Hilbrands, and J. H. Boon. 1997. Influence of salinity and dietary com- position on blood parameter values of hybrid red tilapia, Oreochromis niloticus X 0. mossambicus. Aquaculture Research 28:453-459.

Walker, R. L., P. R. H. Wilkes, and C. M. Wood. 1989. The effects of hypersaline exposure on oxygen-affinity of the blood of the freshwater teleost Catostomus commersoni. Journal of Experimental Biology 142:125-142.

Wedemeyer, G. 1972. Some physiological conse- quences of handling stress in juvenile coho salm-

on, Oncorhynchus kisutch and steelhead trout Sal- mo gairdneri. Journal of the Fisheries Research Board of Canada 29(12):1780-1783.

Wedemeyer, G. A. 1996. Physiology of fish in intensive culture systems. International Thompson Publishing Inc., New York, USA.

Weirich, C. R. and J. R. Tomasso. 1991. Confine- ment and transport-induced stress on red drum juveniles: effect of salinity. Progressive Fish-Cul- turist 53:146-149.

Weirich, C. R., J. R. Tomasso, and T. I. J. Smith. 1992. Confinement and transport-induced stress in white bass X striped bass hybrids: effect of calcium and salinity. Journal of the World Aquacul- ture Society 23:49-57.

Documents

Effects of Salinity on Growth, Survival, and Selected Hematological Parameters of Juvenile Cobia Rachycentron canadum