Probiotics improve survival and growth of larval Pacific Lamprey in laboratory culture

Abstract Objective The Pacific Lamprey Entosphenus tridentatus is a First Food for members of the Confederated Tribes of the Umatilla Indian Reservation and other Columbia Plateau tribes in the Pacific Northwest. Declines in Pacific Lamprey abundance have prompted restoration efforts, including development of artificial propagation. Laboratory rearing of larvae has focused on maximizing survival and growth to conserve resources and increase production. To test the hypothesis that bacterial supplements increased the survival and growth of first‐feeding larval Pacific Lamprey, we conducted two controlled experiments. Methods First, a probiotic supplement (EPI‐CIN G2; Epicore, Bionetworks) was added to a standard food ration (yeast and Otohime mix) at two levels (2 and 5 mg/L) in a replicated, randomized design. Result Growth at 10 weeks was measured, and larvae that were fed probiotics at both levels grew significantly faster (2 mg/L: 11.0 μm/day; 5 mg/L: 13.3 μm/day) than controls that were fed the standard ration alone (6.6 μm/day). Larvae that received the probiotic supplement also had a higher survival (2 mg/L: 36%; 5 mg/L: 44%) than those fed the standard ration (24%). Next, a different cohort of larval lamprey was fed the same two levels of probiotic (at the same rate as in the first experiment), but the lamprey was kept in larger rearing pans and were fed for 28 weeks. Overall growth rates in the second experiment (2 mg/L: 4.6 μm/day; 5 mg/L: 5.7 μm/day; control 3.4 μm/day) were lower than those in the first experiment, but growth and survival (2 mg/L: 71.4%; 5 mg/L: 78.6%; control: 55.7%) were both highest in the treatments with probiotic. Moreover, in both experiments, we observed the highest growth in the probiotic treatments that also had high larval density. Conclusion This suggests that probiotics may help to overcome density‐dependent growth, which is a common problem in lamprey culture. Successful artificial propagation and culture of Pacific Lamprey are vital to the long‐term restoration goals for this imperiled First Food.