Feeding and Growth of Larval Pacific Lamprey Reared in Captivity

Abstract

Pacific Lampreys Entosphenus tridentatus are declining in the Columbia River basin as well as in much of their broader range. To mitigate for reductions in abundance, strategies such as hatchery propagation and captive rearing of lamprey larvae are currently being considered. We conducted a series of experiments using captive larval Pacific Lampreys at Eagle Creek National Fish Hatchery to investigate the effect of different food types and different food concentrations on the growth of larvae. In our first experiment, we evaluated the growth of larvae (TL range, 59–145 mm) given four different food types (algae, leaves, yeast–larval fish food, and salmon carcass analogs) and a control group that was not fed. Assimilation of food types was evaluated by tracking unique stable isotope signatures of δ13C and δ15N within larval tissues. Results from experiment 1 indicated that lampreys fed a diet of salmon carcass analog or algae had positive growth (up to 0.16 mm/d and 42% proportional change in length) over approximately 6 months. Isotopic analyses of larval tissues showed unique signatures that matched those of their specific food treatment. Based on the results of experiment 1, we conducted a second experiment to evaluate the growth of larvae fed four different quantities of salmon carcass analog. Results from this experiment indicated larval growth rate increased with increasing rations of food, but positive growth was observed in all feeding treatments. The highest dose of salmon carcass analog resulted in the highest growth (up to 0.15 mm/d and 36% proportional change in length) over 6 months. We successfully reared larval Pacific Lampreys in captivity with minimal mortality and positive growth, which highlights the potential to use captive rearing and propagation as a conservation tool for this ecologically and culturally important species.

Low Mortality of Larval Lampreys from Electrofishing, Suction-pumping, Anesthesia, and Handling

“…We used Pacific Lamprey that were larvae captivehoused at Eagle Creek National Fish Hatchery for the control trial (see Jolley et al 2015 for description of rearing configuration). We removed 10 larvae from their rearing vessels on 7 July 2015 and placed them in buckets of hatchery water supplied with oxygen for transport to the laboratory at the Columbia River Fish and Wildlife Conservation Office where all survival monitoring trials occurred.…”

“…The electric field under the cover irritates larvae and causes them to emerge from the substrate, where they are pumped to the surface and screened through a collection basket. Although the effect of sampling and handling on larval lamprey has not been explicitly assessed, anecdotal and observational evidence suggests that lamprey are resilient to these activities (Jolley et al 2013;Kurath et al 2013;Jolley et al 2015).…”

Pathogens of Pacific Lamprey Detected Through Routine Fish Health Screenings

“…We used the Clackamas River subbasin as the source of larval Pacific Lamprey for captive-rearing research conducted at Eagle Creek National Fish Hatchery (Jolley et al 2015(Jolley et al , 2017. Eagle Creek National Fish Hatchery is located along Eagle Creek and is within the Clackamas River subbasin ( Figure 2).…”

“…Pacific Lamprey Entosphenus tridentatus abundance in the Pacific Northwest has been declining and conservation actions are underway (Close et al 2002;Luzier et al 2011). Some conservation actions include translocation of wild lampreys to vacant or sparsely populated habitats (Close et al 2009;Ward et al 2012), improving access for migratory fish to new or previously occupied habitats (Keefer et al 2013;Goodman and Reid 2017;Jolley et al 2018), captive rearing (Jolley et al 2015), and artificial propagation (Lampman et al 2016;Clemens et al 2017).…”

Predicting larval metamorphosis of Pacific lamprey Entosphenus tridentatus through measurements of length and mass

“…In addition, existing information on metamorphosis in E. tridentatus is largely from periodic observations of the occurrence of larvae or juveniles in streams (Richards & Beamish, 1981; van de Wetering, 1998). Researchers have developed protocols to rear wild larvae in captivity (see Hanson et al ., 1974; Jolley et al ., 2015) and begun to use tags to mark and follow individual larvae (Hanson & Barron, 2017; Silver et al ., 2009). These techniques have allowed for the evaluation of the metamorphosis of individual larvae under controlled conditions.…”