World Aquaculture September 2018

WWW.WA S.ORG • WORLD AQUACULTURE • SEP TEMBER 2018 61 temperature, although the fatty acid profile of older larvae changed in response to rearing temperature. At lower water temperature, the amount of polyunsaturated fatty acids increased in older larvae, as exemplified by elevated total n-6 fatty acids (Fig. 10), while monounsaturated fatty acid concentrations decreased (Fig. 11). This increase in the degree of unsaturation in coldwater-reared lamprey should increase the fluidity of membranes at low temperatures. Concentrations of specific saturated fatty acids also varied as temperature changed, with lamprey in cold water increasing concentrations of 13- and 15-carbon saturates while reducing the concentrations of 12-, 14- and 16-carbon saturates. Odd-numbered saturates tend to have lower melting points than similar even- numbered saturates (Knothe and Dunn 2009) so their increased concentration in colder water may function to increase membrane fluidity. Conclusions This research demonstrated that larval lamprey can be cultured in water as warm as 22.6 C without increased mortality. To maintain rapid growth, rearing temperature should be around 19.2 C for early larvae and 15.7 C for older larvae. The fatty acid profile of larvae will change in response to rearing temperature and this should be taken into consideration when planning a culture program for lamprey. Fatty acids are a major source of metabolic energy for fishes, serve regulatory functions, are used to synthesize bioactive molecules and are important structural components of cell membranes. Based on changes to the fatty acid profile, younger larvae adapt more rapidly to new rearing temperatures than older larvae. In selecting a culture temperature, it may be beneficial to consider the environmental temperature after fish leave the hatchery. Ultimately this work refined our 14.7 17.3 19.2 22.4 20:5n-3 (% of FAME) 0 2 4 6 Treatment Temperature (°C) a ab a b FIGURE 8. EPA (20:5n-3) 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. Treatment Temperature (°C) 10 12 14 16 18 20 22 24 Mean Wet Weight (mg) 400 450 500 550 600 b b a ab FIGURE 9. Mean wet weight of older larval lamprey reared at different treatment temperatures for 56 days. Error bars represent standard deviation (n = 3). Different letters indicate a significant difference as determined by ANOVA followed by SNK test. 12.3 15.7 19.4 22.6 Total n-6 (% of FAME) 0 2 4 6 8 Treatment Temperature (°C) b a b b FIGURE 10. Total n-6 fatty acid content in the whole body fatty acid profile of older larval Pacific lamprey reared at different treatment temperatures for 56 days. Error bars represent standard deviation (n = 3). Different letters indicate a significant difference as determined by ANOVA followed by SNK test. 12.3 15.7 19.4 22.6 Total MUFA (% of FAME) 36 38 40 42 Treatment Temperature (°C) ab a ab b FIGURE 11. Total mono-unsaturated fatty acid (MUFA) content in the whole body fatty acid profile of older larval Pacific lamprey reared at different treatment temperatures for 56 days. Error bars represent standard deviation (n = 3). Different letters indicate a significant difference as determined by ANOVA followed by SNK test. ( C O N T I N U E D O N P A G E 6 2 )