EFFICACY OF A VACUUM BENTHOS SAMPLER FOR COLLECTING DEMERSAL FISH EGGS FROM GRAVEL SUBSTRATUM

We used two densities of eggs (low = 900 eggs/m(2); high = 5100 eggs/m (2)) in laboratory experiments to estimate the recovery efficiency of the Brown benthos sampler for collecting fish eggs from gravel substra te and to determine if differences (e.g., 5-fold) in egg density in th e substratum could be detected with the sampler. The mean egg recovery efficiency of the sampler in the low and high density treatments was 30% (SE = 8.7) and 35% (SE = 3.8), respectively. The difference betwee n the treatment means was not significant. Therefore, data from the tw o treatments were pooled and used to estimate the recovery efficiency of the sampler (32.7%, SE = 4.4). However, we were able to detect a 5 x difference in the number of eggs collected with the sampler between the two treatments. Our estimate of the recovery efficiency of the sam pler for collecting fish eggs was less than those reported for the sam pler's efficiency for collecting benthic macroinvertebrates. The low r ecovery efficiency of the sampler for collecting fish eggs does not le ssen the utility of the device. Rather, ecologists planning to use the sampler must estimate the recovery efficiency of target fauna, especi ally if density estimates are to be calculated, because recovery effic iency probably is less than 100%.