Smooth Bottom Net Trawl Fishing Gear Effect on - New England ...

NOAA/NMFS Unallied Science Project, Cooperative Agreement NA16FL2264 December 2005
<strong>Smooth</strong> <strong>Bottom</strong> <strong>Net</strong> <strong>Trawl</strong> <strong>Fishing</strong> <strong>Gear</strong> <strong>Effect</strong> on the Seabed:
Investigation of Temporal and Cumulative <strong>Effect</strong>s BKAM/CR
(Langton and Bowman 1981). Other food items include fish eggs, small fish and
vegetation (nearshore).
The size ranges of the targeted flatfish from which stomachs were collected in this trawl
study were similar between species and study sites, about 20 to 40 cm. Stomachs of
yellowtail and winter flounder adults from pre-trawl surveys in August, and post-chronic
trawl surveys in October and November were first sorted into broad taxonomic
categories: annelida, crustacea, molluscs, other invertebrates and unidentifiable stomach
matter.
Some 68 different taxa were identified from fish stomachs. The average density of taxa
collected in yellowtail and blackback flounder stomachs at Mud Hole are listed in Tables
3.6-3 and 3.6-4 and those for the same species at Little Tow in Tables 3.6-5 and 3.6-6.
Raw counts are tabulated in Appendix 3.6-A.
Tables 3.6-7 and 3.6-8 list the 10 most dominant species collected in benthic grab
samples from the experimental lanes and compares these with the most abundant taxa
found in the stomach of fish collected during the same survey period. The August
stomach contents are compared with July benthic infaunal samples. In early August,
there was very little material in the fish stomachs. This might have been related to time
of day or the tide. Handling procedures were the same for all surveys and it appears that
the fish had not been actively feeding just before the trawls were taken. There was an
average of 14.4 to 16.8 individuals of 3.5 to 6.8 species. At Mud Hole, spionids,
probably the species Prionospio steenstrupi and Spio limicola, were the most abundant
organisms in stomachs of yellowtail. All the remaining species groups listed were
polychaetes. For blackbacks, maldanids were the most common prey followed by
spionids. The remaining most common species in the stomachs were all polychaetes with
the exception of cerianthids. Since these anemones were not common in the benthic
faunal samples there must have been some specific selection for this taxon.
At Little Tow, spionids were the most common prey followed by cirratulids and
caprellids. Caprellid amphipods were not common in the benthic samples in 2002. In
2001, the caprellid, Aeginina longicornis, was present in much greater numbers and was
an important component in stomach contents. Spionids were the most numerous group
eaten by blackback flounder followed by aorids, another amphipod taxon, which was
found in fewer numbers in 2002, partly because sites selected for study were those with
finer sediments. Aorids are more abundant on coarse sediments. The bivalve Nucula
delphinodonta, was not listed among the dominants in stomach content analyses although
it was always among the most numerous species at all sites in each sampling period.
Although it is a small bivalve, it is large relative to spionoid polychates and was reported
in the stomachs of both yellowtail and blackback flounder in low numbers.
In October, average numbers of individuals in fish stomachs ranged from 57.7 to 225.6
and the average number of species was 12.5 to 20.5. Spionids were the most numerous
taxon consumed at both Mud Hole and Little Tow. Most of the remaining prey items
were polychaetes with cirratulids, maldanids, ampharetids and phyllodocids very
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