Abstract Title

Session S-03D: Forage Fish Research and Protection in the Salish Sea

Keywords

Species and Food Webs

Start Date

30-4-2014 3:30 PM

End Date

30-4-2014 5:00 PM

Description

Most investigations of intertidal forage fish reproduction have been qualitative, useful for documenting spatio-temporal spawning distributions. Quantitative methods for assessing trends in egg abundance are lacking, however. We began a study at Naval Magazine Indian Island during 2011 to develop a standardized sampling protocol to establish annual indices of surf smelt (Hypomesus pretiosus) and Pacific sand lance (Ammodytes hexapterus) spawning success. A stainless steel quadrat frame was used to remove substrate samples from transects at random points in the +5 to +10 foot tidal elevation range. Samples were later placed in an inverted plastic cone and water pumped upwards (i.e. elutriation) to separate eggs and larvae (hereafter referred to as embryos; EMB) from substrate particles. During the 2011-2012 sample period (Year 1; October-March) we collected approximately 225,000 smelt (mean CPUE, 387 EMB/ft2) and 230,000 sand lance (mean CPUE, 111 EMB/ft2). Catch rates increased during Year 2 (September-April); we collected an estimated 207,000 smelt (mean CPUE, 524 EMB/ft2) and 346,000 sand lance (mean CPUE, 878 EMB/ft2). During Year 1, both smelt (3,731 EMB/ft2) and sand lance (1,823 EMB/ft2) CPUE peaked in November. During Year 2, smelt CPUE peaked in September (3,675 EMB/ft2) and sand lance CPUE peaked in November (4,615 EMB/ft2). Natural mortality of embryos (expressed as the percentage of dead eggs of total catch) appeared much higher for smelt (21% in Year 1, 33% in Year 2) than for sand lance (3% in Year 1, 6% in Year 2). Results from Year 1 indicated moon phase as a potential spawning cue as most young eggs (1/2 coil stage or younger) of both species were captured when the moon was 30% full or less. Similar results were observed in Year 2 with most young eggs of both species occurring when the moon was 40% full or less. The methodologies developed for this study show promise in providing quantitative indices of forage fish spawning success. We are collaborating with the Washington Department of Fish and Wildlife to increase the precision of quantitative indices. Such indices can provide valuable baseline data to evaluate habitat restoration projects, such as bulkhead removals and causeway alterations, in Admiralty Inlet and elsewhere and to monitor the overall population trends of two important prey species.

Share

COinS
 
Apr 30th, 3:30 PM Apr 30th, 5:00 PM

Quantitative Assessment of Intertidal Forage Fish Embryos

Room 611-612

Most investigations of intertidal forage fish reproduction have been qualitative, useful for documenting spatio-temporal spawning distributions. Quantitative methods for assessing trends in egg abundance are lacking, however. We began a study at Naval Magazine Indian Island during 2011 to develop a standardized sampling protocol to establish annual indices of surf smelt (Hypomesus pretiosus) and Pacific sand lance (Ammodytes hexapterus) spawning success. A stainless steel quadrat frame was used to remove substrate samples from transects at random points in the +5 to +10 foot tidal elevation range. Samples were later placed in an inverted plastic cone and water pumped upwards (i.e. elutriation) to separate eggs and larvae (hereafter referred to as embryos; EMB) from substrate particles. During the 2011-2012 sample period (Year 1; October-March) we collected approximately 225,000 smelt (mean CPUE, 387 EMB/ft2) and 230,000 sand lance (mean CPUE, 111 EMB/ft2). Catch rates increased during Year 2 (September-April); we collected an estimated 207,000 smelt (mean CPUE, 524 EMB/ft2) and 346,000 sand lance (mean CPUE, 878 EMB/ft2). During Year 1, both smelt (3,731 EMB/ft2) and sand lance (1,823 EMB/ft2) CPUE peaked in November. During Year 2, smelt CPUE peaked in September (3,675 EMB/ft2) and sand lance CPUE peaked in November (4,615 EMB/ft2). Natural mortality of embryos (expressed as the percentage of dead eggs of total catch) appeared much higher for smelt (21% in Year 1, 33% in Year 2) than for sand lance (3% in Year 1, 6% in Year 2). Results from Year 1 indicated moon phase as a potential spawning cue as most young eggs (1/2 coil stage or younger) of both species were captured when the moon was 30% full or less. Similar results were observed in Year 2 with most young eggs of both species occurring when the moon was 40% full or less. The methodologies developed for this study show promise in providing quantitative indices of forage fish spawning success. We are collaborating with the Washington Department of Fish and Wildlife to increase the precision of quantitative indices. Such indices can provide valuable baseline data to evaluate habitat restoration projects, such as bulkhead removals and causeway alterations, in Admiralty Inlet and elsewhere and to monitor the overall population trends of two important prey species.