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
water column. The beginning of this fall mixing can be seen in the October CTD data.
Mixing is then complete in November, most likely due to the storm.
Rock crab catch and densities at Little Tow were very similar to those for Mud Hole
rising slightly from August to October then falling off in November. Monkfish were only
present at a significant density in August at Little Tow, Lane 1 (2.57 kg/1000m 2 ) then
decline sharply to 0.23kg/1000m 2 in October, and were not present in November.
In August 2002, Little Tow station densities for spiny dogfish were slightly higher than
those seen at Mud Hole but dropped to almost zero in October and stayed low through
November.
3.6.2 Flatfish Metrics and Stomach Content Results
Refer to Figures 3.6-8 to 3.6-11 for length frequency distributions for yellowtail flounder
and winter flounder at Mud Hole and Little Tow. The yellowtail and winter flounder
catch ranged from 16 to 41 cm in length. The length frequency distribution of yellowtail
flounder indicate that the catch was dominated by an age class of two-year-old fish with a
mean size of about 33 cm in August, increasing to 34 cm in November. This increase
shows growth over the study period. A few one- and three-year-old fish are present as
well (NOAA-NMFS EFH source documents). Winter flounder showed a similar shift
from about 9 cm to almost 33 cm, again showing dominance of a second year age class.
The purpose of assessing the stomach contents of the targeted bottom feeding fish, winter
flounder and yellowtail flounder, was to:
Document the diets of these flatfish within the study sites considered Essential
Fish Habitat (EFH);
Determine how the flatfish prey selection may relate to the benthic fauna; and
Explore the potential effects of repeated towing on consumption or diet.
Feeding by yellowtail flounder is generally restricted to benthic macrofauna. Annelids
and arthropods found on the sediment surface constitute large components of the
yellowtail flounder diet. For yellowtail flounder above 5 cm in length, other invertebrates
and fish (e.g., capelin and sand lance) make up most of the remainder. Among
crustaceans, amphipods are the largest diet component.
Winter flounder are generalists that feed on any prey of suitable size encountered while
foraging. Adults have little variation in diet with size. Mouth size is even more restrictive
than in yellowtail. Polychaetes, crustaceans (amphipods and decapods) and mollusks
(bivalves) are identified as important prey by percent incidence and weight for studies in
the Gulf of Maine. Polychaetes were frequently the most important food item on a
percent weight basis and in terms of numbers (Langton and Bowman 1981). Cnidaria
have also been found to be an important component of the adult winter flounder diet
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