Ichthyoplankton samplers for simultaneous replicate samples at surface and bottom

Abstract

Descriptions and illustrations of ichthyoplankton sampling gear which utilize onemeter diameter nets on square and rectangular frames and provide simultaneous surface and bottom samples are presented. Designed for use on boats as small as five meters in length, the gear was developed to provide quantitative and qualitative ichthyoplankton samples from shallow estuarine waters (1–12 m). Data are presented which indicate that filtration performance (in relation to clogging of 505 micron mesh nets), averaged 97% and 103% for the surface and bottom nets respectively. These high filtration rates were attributed to the design of the net frames which apparently act as mouth reducing cones. Catch data for several species from the side-by-side and separated rigs were analyzed with a nested model of analysis of variance. Neither the main effects nor their interactions showed any significant effects. We concluded, therefore, that there is no systematic error inherent in the design of the two samplers which precludes direct comparison of surface and bottom samples taken with them.