In:  Wurts, W. A.  1987.  An evaluation of specific ionic and growth parameters affecting the feasibility of commercially producing red drum (Sciaenops ocellatus).  Doctoral dissertation.  Texas A&M University, College Station, TX.  © 1988


William A. Wurts, State Specialist for Aquaculture

Kentucky State University Cooperative Extension Program




II. High and Low Density Freshwater Pond Feasibility Trials

A. High Density Feasibility Trial

One earthen pond of 0.04 ha and another of 0.1 ha were stocked with juvenile red drum at densities of 11400 and 11300/ha on 1 August 1984 and 25 July 1984, respectively.  Mean weights of fish at stocking were 6.1 g (0.04 ha pond) and 3.7 g (0.1 ha pond).  Tilapia (Tilapia aurea) broodfish averaging approximately 450 g each were stocked in each pond on 28 March 1984 at a density of 630/ha and a ratio of 2:3 male:female.  Filamentous algae was a problem in the 0.1 ha pond; additional sex reversed male tilapia (~ 150 g each) were stocked at 2000/ha as an algae control measure. Floating catfish feed (32% protein) was offered at 5.0% of red drum biomass daily with the rate adjusted on a daily basis assuming a FCR of 1.5 and 90% survival.

Daily temperature and dissolved oxygen readings were recorded for the duration of the study.  Ponds were harvested on 14 November 1984 (0.04 ha pond) and 17 November 1984 (0.1 ha pond) before temperatures reached the lower lethal limits for tilapia.  Individual weights and lengths, mean individual weight, total biomass and mean percent growth for all red drum were determined. Gut contents from approximately 10% of the red drum harvested were identified.  A crude estimate of total biomass (tilapia and red drum) was made.


B. Low Density Feasibility Trial

One 0.04 ha tilapia broodfish pond was stocked with 45 g red drum at 150/ha on 14 July 1984.  After 123 days, red drum were harvested with 100% survival and a mean weight of 396 g (290-550 g).  Based on these results an earthen pond 0.04 ha in surface area was stocked at a density of 490/ha with juvenile red drum, mean weight 35 g, on 14 April 1985.  Tilapia broodfish averaging approximately 150 g each were stocked at a ratio of 1:3 male:female.  In addition, 146 kg/ha of mixed size crawfish were stocked to provide forage for red drum until tilapia fry had become well established.  Floating catfish feed (32% protein) was offered until daily temperatures fell below 15°C. Feeding was arbitrarily fixed at a daily allotment of 16.4 kg/ha for the first 53 days in an attempt to stimulate tilapia reproduction. The rate of feed application was reduced by half for the remainder of the study.

Representative temperature and dissolved oxygen readings were taken three times weekly.  Since an effort to approximate extensive culture conditions was made, no measures were taken to correct for low dissolved oxygen.  Weekly secchi disc readings were taken to assess water clarity.

The study was conducted for 215 days.  Individual weights and lengths, mean individual weight, total biomass and mean percent growth for red drum were obtained and recorded at harvest. Gut contents from all red drum harvested were examined and recorded. An assessment of unexploited tilapia biomass was made.



A. High Density Pond Trial

The ion profile (Table 18) of well water used to fill ponds indicated that there were 1060 mg/l total dissolved solids, 123 mg/l calcium, 30 mg/l magnesium, 87 mg/l chloride and a pH of 7.8.  The lowest single day dissolved oxygen levels were 1.4 and 2.4 mg/l in the 0.04 and 0.1 ha ponds, respectively.  The lowest sustained 3-day dissolved oxygen levels were 2.0 and 4.0 mg/l in the 0.04 and 0.1 ha ponds, respectively.  Mean dissolved oxygen levels were 5.8 (0.04 ha pond) and 6.4 mg/l (0.1 ha pond).  Temperature ranged from 15-31°C with a mean of 25°C.  No fish were observed at the surface during periods of low oxygen.




Ionic profilel of well water used to fill ponds






















lIonic measurements in mg/l.



Red drum survivals at harvest were 9% (0.04 ha pond after 106 days) and 15% (0.1 ha pond after 115 days).  Mean weight and total length of fish from the 0.04 ha pond (42 fish) were 17.8 g (8.5-42.7 g) and 121 mm (98-167 mm). Mean weight and total length for fish from the 0.1 ha pond were 17.7 g (6.2-75.1 g) and 119 mm (89-196 mm) not including 3 of the total 168 which averaged 240 g (195-301 g) and 275 (255-296 mm). The majority (84%) were in the 8-24 g range. 

Red drum increased in weight by 190 and 380% in the 0.04 and 0.1 ha ponds, respectively.  Tilapia biomass (fish 340 g or greater) for each pond was approximately 1350 kg/ha at harvest. It was not feasible to estimate the biomass of smaller tilapia remaining in the mud and grass of pond bottoms; however, considerable numbers of fish were observed. The gut contents of 25 red drum were examined: 16 contained nothing; 5 contained crawfish; 2 contained tilapia fry; 1 contained chironimids; and 1 contained organic material.


B. Low Density Pond Trial

Well water used in this study had the same ionic profile (Table 18) as in the previous pond trial.  Dissolved oxygen in the single 0.04 ha pond ranged from 3.6-9.5 mg/l with a mean of 5.3 mg/l. Temperature ranged from 15-30°C with a mean of 24.5°C.  Secchi disc readings ranged from 23-74 cm with a mean of 34.3 cm.

Red drum survival at harvest (215 days) was 90%.  A single fish was caught 61 days after stocking and weighed 258 g.  After 215 days, red drum had a total biomass of 200 kg/ha and had individual mean weight and total length of 450 g (339-700 g) and 349 mm (310-405 mm). This represents an increase in mean weight of 1190%.  The gut contents of all (18) red drum were examined: 1 contained nothing; 1 contained crawfish only; 5 contained both crawfish and tilapia fry; and 11 contained tilapia fry only.

Tilapia biomass at harvest was 836 kg/ha: 166 kg/ha, brooders with a mean weight of 303 g each; 505 kg/ha, individual tilapia greater than 1.2 g but less than 303 g; and 165 kg/ha, tilapia fry (819 fry/kg).  Tilapia biomass increased by approximately 840%. Less than 11 kg/ha of

crawfish were recovered.



            The results of the freshwater pond culture studies indicated that small red drum (4-6 g) performed poorly (slow growth and high mortality).  Larger red drum fingerlings (35-45 g) displayed rapid growth and good survival.  There are two reasonable explanations for these observations.  Apparently, fish of greater size underwent less osmotic stress and were not food limited.

It is generally recognized that larger animals have both a lower surface area to volume ratio and a lower metabolic rate/unit weight. The gills of fish represent more than 60% of the exposed body surface (Ogawa, 1975).  Large fish would have a lower surface area to volume ratio than small fish with respect to their gills as well as body surfaces. In small fish, more extracellular fluid is brought into close contact with the environment by way of body surfaces.  Therefore, small fish lose relatively more ions to their environment (fresh water) as a result of diffusion across leaky permeability barriers.  This places a greater demand on energy dependent mechanisms of ion homeo­stasis. In addition to osmotic stress, fish are stressed as a result of handling during stocking. Stress can effect the release of cate­cholamines, corticosteroids and possibly pituitary hormones, all of which can affect hydromineral balance (Chan et al., 1968; Guyton, 1971; Johnson, 1973; Sage, 1973; Pic et al., 1974; Shuttleworth, 1978; Pang et al., 1980b; Pang and Yee, 1980; Tomasso et al., 1980; Robertson, 1984). Hence, small fish are subjected to greater osmotic stress due to size (surface area) and higher metabolic rates (greater energy demands). Stress can increase susceptibility to disease, retard growth and cause death (Stickney, 1979).

Second, in the high density pond study, small red drum fry were stocked several months after tilapia broodfish had been stocked.  It is likely that the majority of juvenile tilapia had reached a size too large to be eaten by 4-6 g red drum fry.  The stressors mentioned above were then compounded by food limitation.  It is unlikely that small red drum fry were able to consume large floating feed pellets.  The large fingerlings stocked in the low density pond study were apparently less stressed by handling and osmotic processes and were able to take advantage of the forage base due to their greater size.

In both high and low density pond studies, gut analyses indicated that red drum were consuming juvenile tilapia.  Red drum were observed to chase juvenile tilapia, breaking the water's surface near the pond banks.  However, red drum were never observed to consume floating catfish feed.  Crawfish were present in a relatively large percentage (20-33%) of the fish sampled for gut contents.  This is interesting in that few crawfish were recovered at harvest. Perhaps this indicates a preference for or a greater predatory efficiency on benthic crus­taceans.  The literature concerning red drum food habits tends to substantiate this observation (Pearson, 1929; Simmons and Breuer, 1962; Boothby and Avault, 1971; Bass and Avault, 1975; Overstreet and Heard, 1978).  These studies indicate that shrimp and blue crabs are the most common food items in the diet of red drum.  Many Texas fishermen prefer small live crabs (100 mm or less, carapace width) and 18 g shrimp (live or fresh iced) as red drum baits.

It was noted that one red drum had reached a size of 258 g after 61 days in the low density pond study. Crawfish were stocked (146 kg/ha) just prior to red drum fingerlings.  If one assumes that this single fish was representative of individual mean weight for the entire population, that survival was the same as at harvest, and that all crawfish stocked had been consumed after 61 days, red drum exhibit a wet weight to wet weight food conversion of crawfish to fish biomass of 1.3.  Assuming that crawfish contain a body water content of 70-80%, this represents a dry weight crawfish to wet weight red drum food conversion of 0.3-0.4. This would indicate (Stickney, 1979) that crawfish are an excellent forage/feed for red drum.

The form of the preliminary growth equations from the low density pond study reveals a break or slowing in the growth rate, close to the 258 g size.  This may indicate that red drum were feeding efficiently on crawfish until the crawfish population had been substantially reduced and then began to feed, perhaps less efficiently, on juvenile tilapia.  The results of the low density pond study demonstrate that it is feasible, with adequate food availability, to produce a 450 g red drum in one growing season in fresh water at the latitude of College Station, Texas.  It may be possible to produce a 700-900 g fish in one growing season by improving feeding strategies and stocking earlier in the spring.


For related information click on the topics below:


(view also as PDF) Presented as: Polyculture of largemouth bass (Micropterus salmoides) with blue tilapia (Tilapia aurea): using tilapia progeny as forage. The annual meeting of the U.S. Chapter of the World Aquaculture Society, Hilton Head, SC. Abstract, p. 56. (Unpublished Manuscript)

1993. Journal of the World Aquaculture Society, 24(3): 422-424.


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I gratefully acknowledge Peter W. Perschbacher for his assistance with gut analyses and food item identification.



Chan, D. K. 0., Jones, I. C. and Mosley, W., 1968. Pituitary and adrenocortical factors in the control of the water and electrolyte composition of the freshwater European eel (Anguilla anguilla L.). J. Endocr., 42:91-98.

Bass, R. J. and Avault, J. W., Jr., 1975. Food habits, length-weight relationship, condition factor, and growth of juvenile red drum, Sciaenops ocellata, in Louisiana. Trans. Am. Fish. Soc., 104:35­45.

Boothby, R. N., and Avault, J. W., Jr., 1971.   Food habits, length­weight relationship, and condition factor of the red drum (Sciaenops ocellata) in southeastern Louisiana. Trans. Am. Fish. Soc., 100:290-295.

Guyton, A. C., 1971. A Textbook of Medical Physiology. W. B. Saunders Co., Philadelphia, PA, 1032 pp.

Johnson, D. W., 1973. Endocrine control of hydromineral balance in teleosts. Am. Zool., 13:799-818.

Ogawa, M., 1975. The effects of prolactin, cortisol and calcium-free environment on water influx in isolated gills of Japanese eel, Anguilla japonica. Comp. Biochem. Physiol., 52A:539-543.

Overstreet, R. M, and Heard, R. W., 1978. Food of the red drum, Sciaenops ocellata, from Mississippi Sound. Gulf Research Reports, 6:131-135.

Pang, P. K. T., Kenny, A. D. and Ogura, G., 1980b. Evolution of endocrine control of calcium regulation. In: P. K. T. Pang and A. Epple, (Editors), Evolution of Vertebrate Endocrine Systems. Texas Tech. Univ. Press, Lubbock, TX, pp. 323-356.

Pang, P. K. T. and Yee, J. A., 1980. Evolution of the endocrine control of vertebrate hypercalcemic regulation. In: S. Ishii et al. (Editors), Hormones, Adaptation and Evolution. Japan Sci. Soc. Press. Tokyo, pp. 103-111.

Pearson, J. C., 1929. Natural history and conservation of redfish and other commercial sciaenids on the Texas coast. Bull. U.S. Bur. Fish., 44:129-214.

Pic, P., Mayer-Gostan, N. and Maetz, J., 1974. Branchial effects of epinephrine in the seawater-adapted mullet. I. Water perme­ability. Am. J. Physiol., 226:698-702.

Robertson, L., 1984. Plasma cortisol, glucose and osmolality stress responses in cultured red drum (Sciaenops ocellatus) elicited by handling and transportation and modulation of these responses via anesthetics. Master's thesis, University of Texas at Austin, 101 pp.

Sage, M., 1973. The relationship between the pituitary content of prolactin and blood sodium levels in mullet (Mugil cephalus) transferred from sea water to fresh water. Contrib. Mar. Sci., 17:163-167.

Simmons, E. G. and Breuer, J. P., 1962. A study of redfish, Sciaenops ocellata Linnaeus and black drum, Pogonias cromis Linnaeus. Pub. Inst. Marine Science, University of Texas, 8:184-211.

Shuttleworth, T. J., 1978. The effect of adrenaline on potentials in the isolated gills of the flounder (Platichthys flesus L.). J. Comp. Physiol, 124:129-136.

Stickney, R. R., 1979. Principles of Warmwater Aquaculture. John Wiley and Sons, New York, NY, 375 pp.

Tomasso, J. R., Davis, K. B. and Parker, N. C., 1980. Plasma cortico­steroid and electrolyte dynamics of hybrid striped bass (white bass x striped bass) during netting and hauling.      Proc. World Maricult. Soc., 11:303-310.