"A Contemporary Assessment of the Bycatch of Regulated Species and the Nordmore Grate in the Northern Shrimp Fishery"

Since April 1992, fishermen engaged in this fishery have been required to install a finfish excluder device in their trawl net, known as the Nordmore grate.
(Richards & Hendrickson, 2006).

A data collection program was established using GMRI staff and NOAA observers to monitor and document the bycatch of regulated groundfish and non-regulated species during the 2008-2009 shrimp season. GMRI staff sampled the catch from 137 hauls (tows) over a period of 39 days (fishing trips). Initially four boats were used to collect data, one operating in the waters of northern Massachusetts, one near Boon Is., one in Saco Bay, and another in midcoast Maine. NOAA observers sampled the catch from 106 hauls over 25 fishing trips. The location of each fishing trip sampled by these observers was unknown.

GMRI and NOAA data indicated that the shrimp catch comprised almost 96% and 92% of total catch weight respectively. The proportion of regulated bycatch from both data sources was less than 2% of the total catch weight. In fifty-one percent of all fishing trips sampled by GMRI, regulated species bycatch averaged less than 1% of total catch weight, including all trips from midcoast Maine. In an additional thirty-three percent of fishing trips, regulated bycatch averaged between 1 – 2% of total catch weight. The bycatch of regulated species exceeded 5% of total catch weight in only 5% of hauls, and weighed no more than 55 lbs in any haul. All but one fishing trip sampled by GMRI staff had an average regulated species bycatch of less than 5% per haul. The boat operating in midcoast Maine consistently recorded the lowest proportion of regulated bycatch per haul, while the highest proportions were consistently recorded at Boon Is, particularly in January. Juvenile American plaice comprised almost 50% of regulated species bycatch sampled by GMRI staff. The effect of grate orientation was tested on one boat, but did not appear to alter grate performance.

The bycatch of regulated species did not exceed 5% of total catch weight in any haul sampled by NOAA observers. American plaice similarly dominated the bycatch of regulated species, but only represented 27% of the total catch of this bycatch. Grate orientation had little impact on the proportion or composition of shrimp and regulated bycatch in the total catch. (from final report abstract)

Project goal and objectives
The primary goal of this project was to evaluate the bycatch of regulated groundfish species during the 2008-2009 northern shrimp season and assess the efficacy of the Nordmore grate in reducing the bycatch of regulated groundfish and non-regulated species.

Specific project objectives were to:
1. Monitor and document the bycatch of regulated groundfish and non-regulated species during the 2008-2009 northern shrimp fishing season using GMRI samplers and NOAA observers.
2. Compare the bycatch of regulated species during the 2008-2009 fishing season across spatial and temporal scales.
3. Determine the ability of the Nordmore grate to reduce the bycatch of regulated species to 5% or less of total catch weight.
4. Identify factors affecting the operational performance of the Nordmore grate and compare the catching performance of both upward and downward excluding grates.

shrimp_nordmore_bycatch.csv