Paufve MP, Sethi SA, Lantry BF, Weidel BC, Rudstam LG. Asessing the spawning ecology of fish in situ using a benthic pump sampler. Fisheries Research 214:19-24.
Successful reproduction in fish requires suitable conditions for spawning and egg incubation. Thus, fish species commonly exhibit spawning site selectivity, and understanding habitat requirements to inform population ecology and management relies on in situ observations of eggs. Numerous methods and devices have been developed to sample benthic, non-adhesive fish eggs to relate egg distribution, abundance, and survival to habitat characteristics, yet most do not have estimates of sampling efficiency despite assumptions of imperfect performance. We tested the efficiency of a gasoline-powered diaphragm pump with two different intake nozzle designs by sampling benthic, non-adhesive fish eggs at known densities (50, 200, and 500 eggs m-2) across a range of substrates: silt, gravel, and two depths of cobble. The sampler was ineffective on deep cobble substrate regardless of intake design. However, on substrates with less interstitial space, a narrower intake was consistently effective at detecting the presence of eggs (mean detection probability: 0.92) and demonstrated sufficient egg recovery to detect relative differences in abundance and to estimate absolute abundance with enough repeating samples. On average, 45% of eggs directly beneath the intake were recovered after four minutes of pumping, with most collected during the first two minutes. Eggs were often collected from outside the intake area, increasing variability in egg counts. When these limitations and imperfect efficiencies are accounted for, the pump sampler is uniquely suited for in situ assessment of eggs to inform large-scale spawning site use, small-scale habitat selection, and other applications relevant to spawning ecology.