Characterization of River Herring Bycatch in the Northwest Atlantic Mid-Water Trawl Fisheries

The incidental catch of river herring (alewife and blueback herring) by mid-water trawl vessels targeting Atlantic herring and mackerel has become a concern for their conservation. Reduction of this incidental catch is a focus of fisheries managers, but information about river herring bycatch is limited. We combined port-side and at-sea observations with knowledge of the habits of river herring at-sea to describe the characteristics (species, amount, size, maturity, origin) of river herring caught in various regions of the fishery. Results showed inter-annual, inter-species, and intra-species differences in bycatch between and within each area. Bycatch in the northern areas of the fishery was mainly comprised of migratory mature or near-mature river herring from mixed origins. In contrast, bycatch in the southern areas was a mix of juveniles, pre-spawning adults from nearby areas, and migratory adults. These results suggest the impact of bycatch may vary throughout the range of the fishery and bycatch mitigation strategies should be consistent with this differing impact.