A Method to Reduce Winter Flounder Retention By Minimizing Variability in Drop Chain Performance in the Inshore Loligo Small Mesh Trawl Fishery off Long Island, NY Within the SNE Winter Flounder Stock Area

 

 (Funded by the Commercial Fisheries Research Foundation Challenge Grant Program for Conservation Engineering Projects - Winter Flounder Bycatch Reduction) 

 
 
In 2010 Cornell Marine Program conducted a proof of concept project designed to reduce fishing mortality and bycatch of winter flounder as well as contribute to the rebuilding of the overfished stock by testing an alternative gear strategy. The strategy we employed was use of a 12” drop chain sweep coupled with headrope adjustments.
 
         Illustration of a 12 inch drop chain configuration
 
There are two things that a longer drop chain does that are beneficial to reducing winter flounder catch.  The first is that there is more of a gap between the footrope and the sweep (area of escapement).  Secondly, and more importantly is that a longer space makes it possible to drop the sweep behind the footrope.  The reason that this is important is that with the sweep behind the footrope, the mud cloud created occurs behind the footrope, making the gap between the footrope and the sweep visible for flounders, giving them an escape path.
 
The project design was based on the following hypotheses:
 
•Slacking back the headrope creating more headrope height helps maintain drop chain opening for winter flounder escapement and does not affect the total catch of squid in the net.
 
•By varying the amount of slack in the headrope it is possible to achieve optimum bilateral species impact.
 
•Behavioral analysis of squid reactions have shown that squid display swimming endurance in the forward part of the net.  This suggests that heightening the headrope may improve overall squid capture.
 
This methodology was functionally and conceptually possible based upon preliminary tank experimental work. Add photos. The gear design would be considered successful if it proved to be effective in reducing winter flounder bycatch yet not reduce the harvest of target species to levels below economic viability.
 
A single vessel (F/V Caitlyn and Mairead) was used in this study to conduct replicate tows comparing a control trawl to an experimental trawl. The control trawl was common standard 4 seam trawl fitted with a 12 inch drop chain sweep.  The experimental trawl was the exact same net with the headrope slacked back in increments. The experimental trawl was modified to reflect increases in the amount of slack on top of the trawl.  Lengthening adjustments were made in 6 inch increments from zero (control net) to 3 feet.  We monitored the effects on winter flounder bycatch reduction and retention of the target species. One hour tow durations were used during this study to maximize the number of tows conducted per trip and still remain within the range of commercial tow durations (1-3 hours). The experimental sampling program consisted of four single day fishing trips. We made a minimum of six tows per trip totaling 24 tows for the entire project. 
 
On Board Catch Processing
 
Our goal was to quantify differences in winter flounder retention between control and experimental nets (treatment). As such, total winter flounder for each tow was accurately weighed. Small catches allowed for all winter flounder to be sampled for length frequency. Since Loligo co-occur with the winter flounder, and we were looking at bycatch in the Loligo fishery, the total Loligo catch was also weighed on each tow and a length sample obtained. The total weight of all species in each tow was also recorded by direct weights of the total catch, or for large catches, the entire catch was placed in baskets and a sub-sample of the baskets weighed. Whiting was chosen as an additional priority species relative to its importance to the trawl fishery which may be impacted by winter flounder regulations.  Actual total weights of whiting (Merluccius bilinearis) were obtained but whiting catch overall was minimal.