Effects of temperature on feed intake and plasma chemistry after exhaustive exercise in triploid brown trout (Salmo trutta L)

Abstract

The physiological effect of temperature on feed intake and haematological parameters after exhaustive swimming in diploid and triploid brown trout (Salmo trutta) was investigated. Trout were exposed to an incremental temperature challenge (2 °C/day) from ambient (6 °C) to either 10 or 19 °C. Feed intake profiles did not differ between ploidy at 10 °C; however, triploids had a significantly higher total feed intake at 19 °C. After 24 days, each temperature-ploidy group was exposed to exhaustive swimming for 10 min. The haematological response differed between ploidy, with the magnitude of the response affected by temperature and ploidy. Post-exercise, acid-base and ionic differences were observed. Plasma lactate increased significantly from rest for both temperature and ploidy groups, but glucose increased significantly at higher temperature. Post-exercise, triploids at 19 °C had significantly higher osmolality and cholesterol than diploids, but differences were resumed within 4 h. Elevated alkaline phosphatase (ALP) and aspartate aminotransferase (AST) in fish at higher temperature suggested greater tissue damage; however, both ploidy responded similarly. Despite no significant differences in deformity prevalence, the type and location of deformities observed differed between ploidy (decreased intervertebral space with higher prevalence in tail area and fin regions for diploids, while vertebral compression, fusion in cranial and caudal trunks for triploids). These results suggest triploids have greater appetite than diploids at elevated temperature and that triploids suffer similar blood disturbances after exercise as diploids. These findings have implications for the management of freshwater ecosystems and suggest that stocking triploid brown trout may offer an alternative to diploid brown trout.

Keywords: Blood chemistry; Brown trout; Deformity; Exercise; Temperature; Triploid.

Fig. 1

Feed intake profiles of diploid and triploid brown trout (Salmo trutta L.) during the 24-day trial period. All trout were reared in quadruplicate 455-L freshwater tanks at 6 °C, then acclimated to 10 and 19 °C (2 °C increment/day), then fed to satiation three times daily. Total feed intake per day for 10 °C (a) and 19 °C (b) is the sum of meals 1–3 each day. Asterisk indicates a significant difference between ploidy (GLM, P < 0.05)

Fig. 2

The effect of temperature, ploidy and exhaustive exercise on blood haematology of diploid and triploid brown trout for a lactate, b glucose, c pH and d osmolality levels. Pre-exercise samples are represented at rest. The vertical stripped bar represents the period of 10-min exercise (Ex.). After the exercise protocol, blood samples were collected at time 1, 4 and 24 h post-exercise. At each time point, 20 fish/ploidy/temperature were sampled and expressed as mean ± SE. Different letters indicate significant differences between ploidy at a given time point. Single asterisk indicates a significant difference to resting levels, and double asterisk indicates a significant difference between 1 and 4 h post-exercise within a given ploidy–temperature regime (GLM, P < 0.05)

Fig. 3

The effect of temperature, ploidy and exhaustive exercise on blood haematology of diploid and triploid brown trout for a phosphorus, b cholesterol, c alkaline phosphatase and d aspartate aminotransferase levels. Pre-exercise samples are represented at rest. The vertical stripped bar represents the period of 10-min exercise (Ex.). After the exercise protocol, blood samples were collected at time 1, 4 and 24 h post-exercise. At each time point, 20 fish/ploidy/temperature were sampled and expressed as mean ± SE. Different letters indicate significant differences between ploidy at a given time point. Asterisk indicates a significant difference to resting levels within a given ploidy–temperature regime (GLM, P < 0.05)