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Comparison of Two Ichthyoplankton Sampling Gears with Notes on Microdistribution of Fish Larvae in a Large River
Author(s) -
Gallagher Robert P.,
Conner John V.
Publication year - 1983
Publication title -
transactions of the american fisheries society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.696
H-Index - 86
eISSN - 1548-8659
pISSN - 0002-8487
DOI - 10.1577/1548-8659(1983)112<280:cotisg>2.0.co;2
Subject(s) - daylight , ichthyoplankton , environmental science , water column , hydrology (agriculture) , fishery , sampling (signal processing) , drum , fish <actinopterygii> , oceanography , biology , geology , geography , physics , geotechnical engineering , archaeology , detector , optics
A pilot comparison of two ichthyoplankton sampling gears was conducted in the lower Mississippi River, Louisiana. The two gears were (1) a 1‐m‐diameter conical plankton net towed at the surface and (2) two 0.5‐m‐diameter, bridleless, conical nets pushed at the surface from either side of the bow of a boat. Sampling was conducted on two different days, during light and dark periods, at three stations representing swift surface currents, sluggish currents, and slack water. Ichthyoplankton were more abundant in townet collections at the fastwater station during daylight hours and at the slackwater station at night, whereas pushed nets were more effective at the slackwater station during daylight hours and at the fastwater station at night. Shads Dorosoma spp. and freshwater drum Aplodinotus grunniens accounted for 94% of all fish larvae collected. Relative abundance of shads was greatest in daylight pushnet collections whereas drum were most abundant in daylight townet collections. Major additional trends: (1) shads, particularly protolarvae, were concentrated in the upper 50 cm of the water column in daylight collections, but were more uniformly distributed at night; (2) freshwater drums were more abundant in the 50–100‐cm stratum during daylight collections, but were more uniformly distributed at night; (3) older freshwater drum larvae were more abundant in nighttime collections, whereas protolarvae were more abundant in daylight samples.