World Aquaculture September 2018

60 SEP TEMBER 2018 • WORLD AQUACULTURE • WWW.WA S.ORG in fish and their specific melting points affect the fluidity of cell membranes at different temperatures. As rearing temperature increased, the fatty acid profile of lamprey larvae shifted from longer-chained, unsaturated fatty acids (Fig. 5) to saturated fatty acids (Fig. 6), the latter of which is fluid at warmer temperatures. The shifting fatty acid profiles also included a decline in key fatty acids such as arachidonic acid (ARA; Fig. 7) and eicosapentaenoic acid (EPA; Fig. 8) in larvae raised in warmwater. The changes in fatty acid profile due to rearing temperature in these early larvae is similar to the response seen in other fish species (Andrews and Stickney 1972, Farkas et al. 1980, Neidleman 1987). Mid-Larval Trial (554 DPH) The second trial occurred in the winter and lasted eight weeks. Treatments included average temperatures of 12.3, 15.7, 19.4 and 22.6 C. The treatment range was broader in this trial than in the early larval trial due to the seasonally cooler ambient groundwater temperature. Every tank was stocked with 15 larvae at 554 DPH and an average weight of 156 mg (Fig. 3B). Husbandry was similar to that described for the early larval trial. Survival of older larvae was high (>96 percent) at all rearing temperatures. Once again fish grew rapidly at all rearing temperatures, but the final length and weight of fish raised at 15.7 C were greater than fish raised at warmer temperatures (Fig. 9). Therefore, 15.7 Cmay be an optimal rearing temperature for older larvae. As in the early larval trial, condition factor was not affected by rearing temperature. Total whole-body lipid, although not significantly affected by temperature, was higher in the older larvae, ranging from 4.2 to 5.1 percent among treatment means. The whole-body fatty acid profile in the older larvae was less responsive to temperature compared to the early larvae as there were no differences in total saturates, ARA or EPA due to rearing Treatment Temperature (°C) 14 16 18 20 22 24 Mean Wet Weight (mg) 25 30 35 40 45 50 55 60 65 Treatment Temperature (°C) a a a b FIGURE 4. Mean wet weight of early larval lamprey reared at different treatment temperatures for 42 days. Error bars represent standard deviation (n = 3). Different letters indicate a significant difference as determined by ANOVA followed by SNK test. 14.7 17.3 19.2 22.4 Total LC PUFA (% of FAME) 0 5 10 15 20 25 30 Treatment Temperature (°C) a ab a b FIGURE 5. Total long-chain polyunsaturated fatty acid (LC PUFA) content in the whole body fatty acid profile of early larval Pacific lamprey reared at different treatment temperatures for 42 days. Error bars represent standard deviation (n = 3). Different letters indicate a significant difference as determined by ANOVA followed by SNK test. 14.7 17.3 19.2 22.4 Total Saturates (% of FAME) 0 10 20 30 40 50 a b a b Treatment Temperature (°C) FIGURE 6. Total saturated fatty acid content in the whole body fatty acid profile of early larval Pacific lamprey reared at different treatment temperatures for 42 days. Error bars represent standard deviation (n = 3). Different letters indicate a significant difference as determined by ANOVA followed by SNK test. 14.7 17.3 19.2 22.4 20:4n-6 (% of FAME) 0 2 4 6 8 a b Treatment Temperature (°C) a a FIGURE 7. ARA (20:4n-6) content in the whole body fatty acid profile of early larval Pacific lamprey reared at different treatment temperatures for 42 days. Error bars represent standard deviation (n = 3). Different letters indicate a significant difference as determined by ANOVA followed by SNK test.