Transactions of the American Fisheries Society 120 121-126, 1991
Influence of Water Hardness and Salts
on Survival and
Physiological Characteristics of Striped Bass
during and after Transport1
PATRICIA M. MAZIK
U.S. Fish and Wildlife Service, Southeastern
Fish Cultural Laboratory
Route 3, Post Office Box 86, Marion, Alabama 36756, USA
BILL A. SIMCO
Ecological Research Center, Department of
Memphis State University, Memphis, Tennessee 38152, USA
NICK C. PARKER2
U.S. Fish and Wildlife Service, Southeastern Fish Cultural Laboratory
' From a dissertation submitted by P.
M. Mazik in partial fulfillment of the requirements for the
degree of Doctor of Philosophy, Memphis State University.
2 Present address: U.S. Fish and Wildlife Service, Texas Cooperative Fish and Wildlife Research Unit, Texas Tech University, Lubbock, Texas 79409-2125, USA.
Abstract.Physiological characteristics and survival of striped bass Morone saxatilis were evaluated during, and for 1 month after, transportation from a soft-water hatchery (hardness, 28 mg L) to a hard-water hatchery (hardness, 110 mg/L). Fish were transported and allowed to recover in either 1.0% sodium chloride, 0.1 % calcium chloride, or flesh water. The addition of 1.0% sodium chloride to the transportation and recovery waters increased survival, decreased the rise in plasma cortisol and plasma glucose concentrations, and reduced osmoregulatory dysfunction. The addition of 0.1% calcium chloride to the transport and recovery media or the use of fresh water did not significantly reduce the stress response of striped bass during and after transport. Striped bass had significantly better survival and lower stress response when transported and allowed to recover in 1.0% sodium chloride than when treated in fresh water or 0.1 % calcium chloride, which is generally used in soft-water hatcheries to increase the water hardness.
Striped bass Morone saxatilis migrate from the ocean into fresh water to spawn. Unfavorable environmental conditions (due to changes in pH, salinity, alkalinity, and hardness) in the freshwater spawning areas of the Chesapeake Bay have led to the practice of capturing wild brood fish, artificially spawning them, and raising the fry in hatcheries throughout the southeastern USA for release into public waters (Parker and Miller 1987). Water quality characteristics in hatcheries where fry have been cultured are notably different in salinity, hardness, and alkalinity from those in the Chesapeake Bay (Geiger and Parker 1985). Fish reared in the hatcheries typically have to acclimatize in water with differing characteristics when they are stocked. Water quality at the stocking locations may be extremely different from that in which fish were cultured, and exposure to a change in environmental conditions often induces a stress response in fish.
Potential stressors that cultured fish are subjected to may be acute (e.g., handling) or chronic (e.g., exposure to low levels of nitrite and ammonia or to pathogens) (Donaldson 1981; Wedemeyer and McLeay 1981). The primary responses to stress include increased plasma concentrations of catecholamines (Mazeaud et al. 1977) and corticosteroids (Mazeaud et al. 1977; Strange et al. 1977, 1978; Specker and Schreck 1980; Barton and Peter 1982; Carmichael et al. 1984; Robertson et al. l 988). Secondary effects of stress include changes in physiological characteristics such as hyperglycemia, and osmoregulatory dysfunction (Wedemeyer 1972; Carmichael et al. 1984). The osmoregulatory function in fish involves control of ionic and osmotic balances that may be upset by the stress of handling and transportation (Wedemeyer 1972; Carmichael et al. 1983) or transfer between fresh water and salt water (Bath and Eddy 1979; Eddy and Bath 1979; Eddy 1981). Freshwater fish transported in salt water that was nearly isotonic with fish blood had lower plasma cortisol and glucose concentrations than fish transported in fresh water (Tomasso et al. 1980; Nikinmaa et al. 1983; Carmichael et al. 1984); they also had increased survival (Long et al. 1977; Johnson and Metcalf 1982). The salt (NaCl) seemingly alleviated osmoregulatory dysfunction by decreasing the osmotic gradient between the transport medium and fish blood.
A solution of 1.0% sodium chloride (NaCl) has been reported to alleviate stress on hybrid striped bass M. saxatilis x M. chrysops (Tomasso et al. 1980). Wedemeyer (1972) recommended that calcium chloride (CaCl2) be added to increase total hardness as calcium carbonate (CaCO3) to at least 50 mg/L. Grizzle et al. (1985) reported that using CaCl2 to increase the hardness of pond water from 10 mg/L to 70-200 mg/L as CaCO3 significantly increased the survival of striped bass.
Observations at the Southeastern Fish Cultural Laboratory have indicated that striped bass stocked at our facility from a hatchery with very soft water, such as Warm Springs National Fish Hatchery, Warm Springs, Georgia, have a very low survival rate. Fish have typically been transported in salt (0.5-1.0% NaCl) and stocked into fresh water at our laboratory. Our objective was to determine the effects of NaCl and CaCl2 on survival and selected hormonal and osmoregulatory stress responses of striped bass transported from a soft-water to a hard-water hatchery and allowed to recover for 1 month in the above salts.
Striped bass (mean, 72 g; SE, 2.5 g) for this study were transported from the Warm Springs National Fish Hatchery (WSNFH) to the Southeastern Fish Cultural Laboratory (SFCL). Physicochemical characteristics of the water at the WSNFH and the SFCL, respectively, were: pH 7.2, 7.4; hardness (mg/L as CaCO3) 28, 110; alkalinity (mg/L as CaCO3) 32, 106; and chloride (mg/L) 27.4, 39.1. Dissolved oxygen exceeded 7.0 mg/L; nitrite and ammonia levels were less than 0.01 mg L at both facilities.
In accordance with standard procedures at the WSNFH, striped bass were harvested from ponds 24 h prior to transport and held overnight in concrete raceways. Fish were handled at WSNFH in a solution of 0.5% NaCl and 0.02% CaCl2. Immediately prior to transport, the fish were loaded into three 1,368-L hauling tanks at a density of 0.18 kg/L. During the 5-h transport, fish were held in three separate, duplicated treatments: (1) 1.0% NaCl, (2) 0.1 % CaCl2, and (3) fresh soft water from the WSNFH. The concentration of 0.1% CaCl2 was used in the present study because it increased total hardness of the water to 220 mg/L as CaCO3. Water quality characteristics during transport were: temperature 12°C, pH 7.1, dissolved oxygen greater than 7.5 mg/L, and nitrite and ammonia less than 0.01 mg/L. Upon completion of transportation, 100 fish were stocked into each of six 1,200-L fiberglass tanks containing hard water with the same additives as in the water in which they were transported. Water from each tank was circulated through a separate biological filter. Water quality characteristics were measured throughout the study; except for salinity, they varied only slightly from those typical at the SFCL. Over the l-month study, temperature gradually increased from 12 to 20°C.
Ten fish were sampled before loading (pre-haul) at the WSNFH. After transport, five fish from each recovery tank were sampled at 0, 3, 6, 9, 12, 24, 48, 72, and 96 h, and at 1, 2, 3, and 4 weeks. All fish were anesthetized in a 0.02% solution of tricaine before blood was collected in ammonia-heparinized syringes from vessels in the caudal peduncle. Sampling was completed within 5 min after initial disturbance and each fish was bled only once. Blood was centrifuged and the plasma was stored at20°C until analyzed. The surviving fish were counted during each sampling period to determine percent survival. We determined plasma concentrations of cortisol, the dominant corticosteroid in fish (Donaldson 1981), by radioimmunoassay using a commercially prepared kit (Serono Diagnostics); plasma glucose with a clinical kit (Sigma Chemical Company); plasma chloride by amperometric-coulometric titration (American Instrument Company); plasma sodium with a flame photometer (Perkin-Elmer); and plasma potassium and calcium by atomic absorption spectrophotometry (Perkin-Elmer).
The data are presented as means ± SE unless stated otherwise. Analyses of variance and Duncan's multiple-range tests (procedure GLM, SAS 1985) were used to test for differences between replicates and among treatments. The level of significance established in all tests was P £ 0.05.
No mortality occurred during transportation, but survival during recovery varied among treatments (Figure 1). The presence of 1.0% NaCl resulted in 100% survival throughout the study. Survival in 0.1% CaCI2 and fresh water decreased at similar rates after 12 h of recovery.
In general, the plasma cortisol concentrations in fish held in 1.0% NaCl during transportation and recovery remained significantly lower than those in fish held in 0.1% CaC12 or in fresh water (Figure 2). Concentrations in fish in 1.0% NaCl did not change significantly during transportation; after 9 h of recovery they were significantly lower than pre-haul levels. Plasma cortisol concentrations in fish in 0.1% CaCI2 and fresh water increased significantly from pre-haul levels during transportation and did not return to pre-haul levels until after 12 h of recovery (Figure 2). After 1 week of recovery, cortisol levels of both groups returned to concentrations similar to those of fish in 1.0% NaCl.
FIGURE 1.Percent survival of striped bass during hauling and recovery for 1 month in either 1.0% NaCl, 0.1% CaCl2, or fresh water in duplicate. Fish were hauled at a density of 0.18 kg/L for 5 h in soft water (28 mg/L hardness) and allowed to recover in hard water (110 mg/L hardness). Temperature during the haul was 12° C; it was gradually increased to 20° C during the 4 weeks of recovery; P represents pre-haul conditions.
Plasma glucose concentrations in fish during transportation and recovery remained significantly lower in the 1.0% NaCl treatment than in the 0.1% CaC12 or fresh water treatments. Concentrations decreased significantly from pre-haul levels during transportation and recovery and were significantly lower than those in fish of the other two groups (Figure 2). Plasma glucose concentrations in fish in the 0.1% CaCI2 and freshwater treatments increased significantly from pre-haul levels during transportation and did not return to these levels until after 96 h and 1 week of recovery, respectively.
Plasma electrolyte concentrations varied during transportation and recovery in the three treatments. Plasma chloride and sodium concentrations in fish in 1.0% NaCl increased significantly from pre-haul levels during transportation and recovery and were significantly higher for the entire study than were levels in fish in the other two treatments (Figures 2, 3). Plasma chloride and plasma sodium concentrations in fish in 0.1% CaCl2 and fresh water decreased significantly from pre-haul levels during transportation. With the exception of plasma chloride in fish in fresh water, which remained below pre-haul levels throughout the study, chloride and sodium levels in plasma of fish in 0.1% CaCl2 and fresh water did not return to pre-haul concentrations until after 1 week of recovery. Plasma potassium concentrations in fish in 1.0% NaCl were significantly lower than pre-haul levels after 3 h of recovery and remained significantly lower than the other two treatments (Figure 3). Plasma potassium concentrations in fish in 0.1% CaCl2 and fresh water did not differ significantly from each other over the l-month study. Plasma calcium concentrations increased from 1.3 to 4.2 meq/L over 1 month. but did not differ significantly among the three treatments (Figure 3).
FIGURE 2.Plasma cortisol, glucose, and chloride (mean ± SE; N = 10) in striped bass during hauling and recovery for 1 month in either 1.0% NaCl, 0.1% CaCl2, or fresh water in duplicate. See Figure 1 caption for details of experimental conditions.
FIGURE 3.Plasma sodium, potassium, and calcium (mean ± SE; N = 10) in striped bass during hauling and recovery for 1 month in either 1.0% NaCl, 0.1% CaCl2, or fresh water in duplicate. See Figure 1 caption for details of experimental conditions.
Handling and transportation are stressful to fish and can result in high mortality, elevated plasma cortisol, hyperglycemia, and plasma electrolyte imbalances (Wedemeyer 1972; Strange and Schreck 1978; Tomasso et al. 1980; Carmichael et al. 1983, 1984; Davis and Parker 1983, 1986; Nikinmaa et al. 1983; Robertson et al. 1988).The use of NaCl has increased survival of fish during transportation (McCraren and Millard 1978; Johnson and Metcalf 1982; Carmichael et al. 1984) and also decreased the effect of stressors (Wedemeyer 1972; Nikinmaa et al. 1983). However, almost any change in environmental conditions, including the addition of chemicals such as salts and anesthetics, may elicit a stress response (Strange and Schreck 1978; Barton et al. 1980; Davis et al. 1982). In our study, plasma cortisol concentrations in striped bass transported and allowed to recover in 1.0% NaCl were similar to those in hybrid striped bass (Tomasso et al. 1980) after transport and recovery in 1.0% NaCl and in red drum Sciaenops ocellatus (Robertson et al. 1988) transported and allowed to recover in 4% and 32% seawater. Plasma cortisol concentrations in striped bass before transportation (pre-haul) were elevated (250 ng/mL) compared to the range for plasma cortisol (0-125 ng/mL) in striped bass observed by Tisa et al. (1983). These elevated concentrations were probably the result of stress from harvesting the previous day. The significantly higher plasma cortisol levels that were observed in fish in 0.1% CaCl2 and fresh water indicated that a severe stress response to handling and transportation occurred in these media.
In our study, plasma glucose concentrations in striped bass transported and allowed to recover in 1.0% NaCl were comparable to those reported for red drum (Robertson et al. 1988) after transportation and recovery in 4 and 32% seawater, and for largemouth bass Micropterus salmoides (Carmichael et al. 1984) transported and allowed to recover in solutions approximating physiological saline (combinations of sodium and potassium chloride, potassium phosphate, and magnesium sulfate) and anesthetic. In striped bass in 1.0% NaCl, the decrease in plasma glucose from prehaul levels indicated that the fish were not stressed during transportation. Plasma glucose concentrations in striped bass in 0.1 % CaCl2 and fresh water were twice as high as levels reported for smallmouth bass Micropterus dolomieui after 2.5 h of transportation (Carmichael et al. 1983). The high plasma glucose in striped bass in 0.1 % CaCl2and fresh water may have been a result of combined stress from transportation and transfer from soft water to hard water. Corticosteroids were elevated in striped bass by exposure to 1.0% NaCl and further increased when fish were additionally stressed by handling (Davis et al. 1982).
Osmoregulatory dysfunction has been well documented as a secondary response to stress (Miles et al. 1974; Mazeaud et al. 1977; Eddy 1981). Plasma chloride and sodium decreased during handling and transportation of smallmouth bass (Carmichael et al. 1983) and brown trout Salmo trutta (Nikinmaa et al. 1983). Carmichael et al. (1983) also reported an increase in plasma potassium during handling and transportation. The presence of 1.0% NaCl apparently prevented changes in plasma electrolytes caused by handling and transportation. Its presence in the transportation and recovery waters may help alleviate osmoregulatory dysfunction by decreasing the osmotic gradient between the plasma and environment, resulting in reduced energy costs for osmoregulation (Reading and Schreck 1983). However, osmoregulatory dysfunction was not inhibited in fish transported or allowed to recover in 0.1% CaCl2 or fresh water, indicating a stress response in these fish.
Cortisol has been reported to increase water influx and ion efflux in a variety of fish species (see reviews by Donaldson 1981 and Mazeaud and Mazeaud 1981). The increase in plasma cortisol concentrations in striped bass in 0.1% CaCl2 and fresh water may explain the problem of maintaining stable electrolyte levels in these media during transportation or recovery. The similarity in concentrations of plasma cortisol, glucose, and electrolytes in fish in 0.1% CaCl2 and fresh water indicated that this concentration of CaCl2 was too low to provide a significant reduction in the physiological responses to transport.
Fish are able to maintain plasma calcium concentrations within a narrow range under a wide variety of conditions (Andreasen 1985; Hunn 1985). Our results indicate that striped bass are also able to maintain plasma calcium levels during periods of primary stress and osmoregulatory dysfunction. Grizzle et al. (1985) reported increased plasma calcium levels in striped bass following the addition of calcium to soft-water ponds. We believe that the increase in plasma calcium concentrations in striped bass over the 1-month recovery period was due to the higher calcium levels in the water at the SFCL compared to that at WSNFH.
Striped bass had better survival and a lower stress response when transported and allowed to recover in 1.0% NaCl, compared to treatments with 0.1 % CaCl2 or fresh water. Because hatchery-reared fish are stocked in fresh water and water with various salinities, striped bass from a softwater hatchery that are transported and allowed to recover in 1.0% NaCl (or in brackish water such as in the Chesapeake Bay) may have significantly increased survival in comparison to those fish transported and allowed to recover only in fresh water. It is not always feasible to both transport and hold striped bass in salt (NaCl) or brackish water (when the fish will be stocked in freshwater reservoirs, for example), so future research is needed to determine the influence of receiving water salinity and the extent to which survival is influenced by the acclimation history or strain of fish being stocked.
We thank K. B. Davis, T. K. Gartner, and J. R. Tomasso for critically reviewing the manuscript. Fish were obtained from the Warm Springs National Fish Hatchery, Warm Springs, Georgia. Mention of trade names or manufacturers does not imply endorsement of commercial products by the U.S. Government.
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Received December 1, 1989 Accepted June 29, 1990