Proposed Abstract Title

Annual Indices of Inter-tidal Forage Fish Spawn Deposition in Kilisut Harbor, Puget Sound

Type of Presentation

Poster

Session Title

Forage Fish Management and Conservation in the Salish Sea

Location

2016SSEC

Description

We sampled beaches in Kilisut Harbor, Puget Sound from October 2011 to March 2015 (four study years) to establish annual indices of surf smelt (Hypomesus pretiosus) and Pacific sand lance (Ammodytes hexapterus) spawn densities. A core sampler was used to retrieve samples from the upper inter-tidal zone of known spawning sites during semi-lunar tides. Incubating embryos (EMB) were separated from substrates using an elutriation process. Smelt EMB densities during Year 4 (mean, 95% confidence interval of 173 ± 46 EMB/ft2) were considerably lower than previous years (Years 1-3 mean of 699 EMB/ft2). Conversely, sand lance densities during Year 4 (1,363 ± 936 EMB/ft2) were higher than those of the first three study years (714 EMB/ft2). Relative precision (RP) of the 95% confidence interval for total annual density averages of smelt during Year 4 (RP 26.6%) was comparable to previous years (average RP 27.6%). Conversely, estimates of sand lance densities during Year 4 (RP 68.6%) were less precise than those observed during previous years (average RP 32.3%). Spawn deposition of both species was found at similar tidal elevations but sites with finer substrates yielded higher sand lance densities. In all four years, sand lance densities peaked in November whereas month of peak smelt density varied by year. Moreover, total annual densities of smelt embryos showed much less inter-annual variation than did those for sand lance. Possible explanations for these results may include differences in site fidelity and spawning cues between species. A more direct explanation for differences in inter-annual catch rates is that our indices are reflecting differences in overall abundance between species among years. A longer time series of data will help clarify whether or not changes in annual egg deposition of the two species moves in tandem or if other interspecific factors are involved.

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Annual Indices of Inter-tidal Forage Fish Spawn Deposition in Kilisut Harbor, Puget Sound

2016SSEC

We sampled beaches in Kilisut Harbor, Puget Sound from October 2011 to March 2015 (four study years) to establish annual indices of surf smelt (Hypomesus pretiosus) and Pacific sand lance (Ammodytes hexapterus) spawn densities. A core sampler was used to retrieve samples from the upper inter-tidal zone of known spawning sites during semi-lunar tides. Incubating embryos (EMB) were separated from substrates using an elutriation process. Smelt EMB densities during Year 4 (mean, 95% confidence interval of 173 ± 46 EMB/ft2) were considerably lower than previous years (Years 1-3 mean of 699 EMB/ft2). Conversely, sand lance densities during Year 4 (1,363 ± 936 EMB/ft2) were higher than those of the first three study years (714 EMB/ft2). Relative precision (RP) of the 95% confidence interval for total annual density averages of smelt during Year 4 (RP 26.6%) was comparable to previous years (average RP 27.6%). Conversely, estimates of sand lance densities during Year 4 (RP 68.6%) were less precise than those observed during previous years (average RP 32.3%). Spawn deposition of both species was found at similar tidal elevations but sites with finer substrates yielded higher sand lance densities. In all four years, sand lance densities peaked in November whereas month of peak smelt density varied by year. Moreover, total annual densities of smelt embryos showed much less inter-annual variation than did those for sand lance. Possible explanations for these results may include differences in site fidelity and spawning cues between species. A more direct explanation for differences in inter-annual catch rates is that our indices are reflecting differences in overall abundance between species among years. A longer time series of data will help clarify whether or not changes in annual egg deposition of the two species moves in tandem or if other interspecific factors are involved.