Early Pacific Sandlance Life History & Survival

This project completed two studies of the ecology of Pacific Sand Lance, a forage fish that recent research has identified as second only to Pacific Herring in its dietary importance for Puget Sound origin Chinook salmon, both juvenile migrants and resident adults, as well as marine birds in the central Salish Sea. Our first study investigated the diet of sand lances collected in the San Juan Islands over several years, comparing gut contents to the prey field--that is, the plankton , a community collected from the same waters, which were sampled and identified in cooperation with WDFW and the Keister lab at the University of Washington. Sand lances were collected by beach seine at least monthly from 2017 to 2020 at Watmough Bay on Lopez Island, in a nearshore area frequented by juvenile Chinook, resident Blackmouth Chinook, and marine birds including Marbled Murrelets. Dissection and prey identification at our Lopez Island laboratory determined that while Pacific Sand Lance feed predominantly on Calanoid Copepods, they select strongly for the larger genera (Eucalanus, Neocalanus) that are present only seasonally in the upper water column, and are strongly influenced by ocean climate. We were also able to determine that larvaceans (free swimming pelagic tunicates) are also seasonally important as prey for sand lances, and are targeted heavily when present. In addition, we were surprised to discover that in late summer, when larger copepods and larvaceans largely disappear, sand lances often feast on large diatoms--a previously undocumented seasonal herbivory. In addition to explaining how the abundance of Pacific Sand Lance could be impacted by climate change in the Salish Sea, our study established a baseline and protocols for monitoring sand lance diet and growth in future. Results of this study were presented in April 2020 to the PSEMP Forage Fish and Food Webs Work Group, and to the [virtual] Salish Sea Ecosystem Conference. Our presentation has been attached to this report, and will be modified as a submission for peer-reviewed publication.
Our second study explored the population structure of Pacific Sand Lance in the Salish Sea, working from our own collections of juvenile and adult fish from Watmough Bay, and others collections of these fish from seven other sites in the south Sound, Admiralty Inlet, the Strait of Georgia, and the Gulf of Georgia. DNA was extracted from fish samples and amplified with primers for 12 microsatellite loci derived from previously published genetic studies of Ammodytes personatus and Ammodytes japonicus in the Gulf of Alaska and Sea of Japan. No population clusters were evident, suggesting that all of the sand lances of the Salish Sea (and perhaps a larger geographical area) are a single panmictic population, and that there exist no spawning beaches that are repeatedly utilized by the same individuals. Heterozygosity was very high, and somewhat lower than predicted for a fully panmictic population by Hardy=Weinberg equilibrium. This indicates that the effective population is very large (once again, possibly extending beyond the Salish Sea) and at the same time, not perfectly panmictic but rather that gene flow is restricted to some small extent over its geographic range. Principal Components Analysis of genotypes from the 229 fish in this study revealed that some alleles tended to cluster (albeit weakly) with the location and year of fishes capture. This may represent the effect of schooling, and the reported tendency of schools to spawn together repeatedly over many years. The bottom line was that Salish Sea sand lances display no long-term fidelity to particular spawning beaches, such as would result in discrete genetic sub-populations.

Baselines for seasonal diet and prey selectivity; and for genetic diversity and population structure; were completed, and protocols and local capacity for future monitoring of these variables were validated