Juvenile Shortnose Sturgeon Acipenser Brevirostrum Research Articles

Oxygen consumption and haematology of juvenile shortnose sturgeonAcipenser brevirostrumduring an acute 24 h saltwater challenge

This study focused on the acute physiological responses to saltwater exposure in juvenile shortnose sturgeon Acipenser brevirostrum. In two separate laboratory experiments, 2 year-old A. brevirostrum were exposed to either full (32) or half-strength (16) seawater for up to 24 h. First, oxygen consumption rates were used to estimate the metabolic costs over 24 h. Secondly, blood and muscle samples were analysed at 6, 12 and 24 h for water loss, various measures of osmoregulatory status (plasma osmolality and ions) and other standard haematological variables. Juveniles exposed to full-strength seawater showed significant decreases in oxygen consumption rates during the 24 h exposure. Furthermore, seawater-exposed fish had significantly increased plasma osmolality, ions (Na(+) and Cl(-)) and a 17% decrease in total wet mass over the 24 h exposure period. To a lesser extent, increases in osmolality, ions and mass loss were observed in fish exposed to half-strength seawater but no changes to oxygen consumption. Cortisol was also significantly increased in fish exposed to full-strength seawater. While plasma protein was elevated following 24 h in full-strength seawater, haemoglobin, haematocrit and plasma glucose levels did not change with increased salinity. These results imply an inability of juvenile A. brevirostrum to regulate water and ions in full-strength seawater within 24 h. Nonetheless, no mortality occurred in any exposure, suggesting that juvenile A. brevirostrum can tolerate short periods in saline environments.

The influence of flume length and group size on swimming performance in shortnose sturgeon Acipenser brevirostrum

The main objectives of this study were to determine optimal methodologies to assess the general swimming performance of juvenile shortnose sturgeon Acipenser brevirostrum. Swimming densities (group v. individual swimming) and flume length (2 v. 1 m) were altered to verify if any of those variables affected performance (i.e. time to fatigue) during critical swimming (U(crit)) and endurance tests. Results for both U(crit) and endurance swimming were not significantly different between fish swum in groups of five or fish swum individually. The U(crit) values, however, were c. 22% higher for fish swum in a longer flume. Although swimming fish in groups did not improve swimming performance, group swimming lowered the variance of the data. Results also reveal that juvenile A. brevirostrum may not possess an ability to swim at high speeds (i.e. burst phase) for long periods.

Behaviour and performance of juvenile shortnose sturgeon Acipenser brevirostrum at different water velocities

Critical swimming speeds (mean +/-s.e.) for juvenile shortnose sturgeon Acipenser brevirostrum were 34.4 cm s(-1)+/- 1.7 (2.18 +/- 0.09 body lengths, BL s(-1)). Swimming challenges at 10, 20 and 30 cm s(-1) revealed that juvenile A. brevirostrum are relatively poor swimmers, and that the fish did not significantly modify their swimming behaviour, although they spent more time substratum skimming (i.e. contact with flume floor) at 30 cm s(-1) relative to 10 cm s(-1). When present, these behavioural responses are probably related to morphological features, such as flattened rostrum, large pectoral fins, flattened body shape and heterocercal tail, and may be important to reduce the costs of swimming.

Metabolic responses to salinity acclimation in juvenile shortnose sturgeon Acipenser brevirostrum

The influence of salinity on the metabolic processes was investigated in the shortnose sturgeon Acipenser brevirostrum . Hatchery-reared juveniles (mean 274 g, 16 months old) were cultured at 18 °C for 10 weeks at salinities of 0‰, 5‰, 10‰ and 20‰. Plasma ions and metabolites were measured to assess the osmoregulatory and metabolic status of the fish through the experimental period. At the conclusion of the trial, metabolic enzymes were measured in several tissues, as were gill and intestinal Na + K + -ATPase in fish cultured at 0‰ and 20‰. In addition, tissue proximate analysis was performed on the white muscle of fish cultured at 0‰ and 20‰. An initial change in plasma osmolality was observed in those fish cultured at the higher salinities (10‰ and 20‰), followed by a return to values observed in fresh water acclimated fish. No significant changes were observed in total plasma free amino acid (FAA) concentrations. Changes were observed in individual amino acid concentrations, some of which may be related to an increased demand for oxidizable substrates in fish exposed to seawater. Total non-esterified fatty acid (NEFA) concentrations were elevated initially in the fish cultured at 20‰ compared with those cultured in fresh water (1732.1±288.1 and 1060.5±119.7 nmol/ml). The proximate analysis revealed a lower white muscle lipid level in fish cultured at 20‰ compared to fish cultured in fresh water (1.1±0.1% and 2.1±0.5%). This suggests that lipids are important in meeting the energetic demands of salinity exposure. An oxidative enzyme (cytochrome- c oxidase) was lower in the gills of fish cultured at 20‰, indicating a decreased aerobic capacity of the gill.

Retention of Coded Wire Tags in Juvenile Shortnose Sturgeon

Abstract We injected 50 juvenile shortnose sturgeon Acipenser brevirostrum with sequentially numbered, standard-length, binary coded wire tags, 4 along each pectoral fin spinous ray, 1 in the base of each pectoral fin, and 1 in the base of the dorsal fin, for a total of 11 tags per fish. After 120 d, the fish were examined for tag retention at each location by means of X-rays. Retention was 98% in the dorsal fin base, 96% in the pectoral fin bases, and 78% in the pectoral fin spinous rays. However, a mean of 6.5 pectoral fin spinous ray tags per fish were retained and all fish retained at least 2 tags. Because individual tags may be recovered nonlethally by taking incremental segments of the spinous ray, the process can be repeated, thus allowing for multiple recaptures. This may be especially important for population studies on endangered species such as the shortnose sturgeon.