Background: Little is known of the larval biology of Pacific lamprey (Entosphenus tridentatus), a species of conservation concern. With miniaturization of passive integrated transponder (PIT) tags, researchers now have the potential to individually mark larval lamprey. However, recent studies with sea lamprey (Petromyzon marinus) ammocoetes indicated that mortality was unacceptably high after surgical implantation of these tags. We examined survival, tag retention, growth, and swimming performance of Pacific lamprey ammocoetes tagged with uniquely coded 8.4-mm PIT tags and controls marked with visible implant elastomer (VIE).Results: Ammocoetes as small as 71 mm in length were PIT-tagged. Of the 99 PIT-tagged individuals, four died (4%) and two lost their tags (2%) within 2 months of tagging. In this period, controls had 5% mortality and 15% VIE mark loss. Incisions were completely healed within 3 months of tagging, and mean specific growth rate during this period did not significantly differ between treatment groups. Ammocoetes bearing a PIT tag did not exhibit significant reductions in swimming performance relative to controls.
Conclusions:We attribute the success of this tagging effort to changes in tag implantation technique, including use of a lateral incision and no sutures. The ability to individually mark wild larval lamprey will allow research on individual growth rates, environmental effects on growth and metamorphosis, timing and rates of movement, and, ultimately, stage-specific survival.
The recent declines in eastern North American species of freshwater mussels have been well documented, but the status of western species has been comparatively understudied. However, various local and regional studies and anecdotal observations indicate that western mussels are also declining, suggesting the need for range-wide assessments of extinction risk and changes in freshwater mussel distributions. Using historic (pre-1990) and recent (1990-2015) occurrence data from across western states and incorporating observations of recent population dynamics, we assessed the extinction risk of western freshwater mussels according to the categories and criteria of the International Union for Conservation of Nature (IUCN) Red List. Percent change in occupied watersheds (by area) between historic and recent time periods was evaluated against IUCN-established thresholds. Additionally, we considered whether evidence of declines was also supported by reported observations of changes in abundance or occurrence in studied water bodies, watersheds, or regions. We also assessed the proportion of watersheds that have reduced species richness as compared with historic levels. We evaluated four western freshwater mussel taxonomic entities: three currently recognized species and one clade consisting of two currently recognized species. Of the four entities assessed, two are Vulnerable (Anodonta nuttalliana and Gonidea angulata), one is Near Threatened (Margaritifera falcata), and one is Least Concern (Anodonta oregonensis/kennerlyi clade). Freshwater mussel richness declined 35% across western watersheds by area, and among the most historically diverse watersheds, nearly half now support fewer species/clades. Future research and conservation efforts should prioritize identifying the proximate causes for these declines and preserving existing habitat and populations.
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