Quantifying and describing river herring bycatch in the U.S. northwest-Atlantic herring and mackerel trawl fisheries

No abstracts are to be cited without prior reference to the author.

In the U.S. northwest Atlantic, the incidental catch of river herring (Alosa pseudoharengus, A.aestivalis) by mid-water trawl vessels targeting Atlantic herring (Clupea harengus) and mackerel (Scomber scombrus) has become a concern for their conservation. Information about this bycatch is limited to length frequencies and weight estimates across broad areas. In response, managers have proposed increasing atsea observer coverage to 100%, but this sampling rate may be fiscally impossible. By combining port-side and at-sea observations, we show that information about river herring bycatch can be improved without substantially increasing at-sea observer levels. We generated length distributions, maturity estimates, weights, and number of river herring caught for four near shore areas. We showed intra- and interspecies differences for these attributes between and within the areas of focus. These characteristics were also used to evaluate the potential impact of bycatch each area. Weight estimates for 2011 and 2012, generated through a ratio estimator, had coefficients of variation (CVs) mostly close to or below 0.3, with none exceeding 0.6. Based on these results and the cost of 100% at-sea observer coverage, improvements to and coordination between port-side and at-sea sampling programs may be the best scheme to improve information on river herring bycatch.