Research Document - 2015/035

Evaluation of Fishery Independent Surveys as Assessment Tools for Lobster Fishing Areas (LFAs) 34-38

By D.S. Pezzack, M.J. Tremblay and C.M. Denton

Abstract

Fishery-independent data are needed to fully assess lobster stock status in the Maritimes Region. In the areas covered by Lobster Fishing Areas (LFAs) 34-38, there have been several types of surveys that were designed to target other species. These surveys are the Fisheries and Oceans Canada (DFO) Maritimes Region Summer Research Vessel Survey (RV survey), an industry-sponsored survey for groundfish (Individual Transferrable Quota, or ITQ survey) and several surveys for scallops (Scallop surveys).  All three survey types collected data on lobster abundance and demography. Because of differences in gear selectivity and survey timing, the surveys provide a different window on the population than that provided by commercial traps. This document includes survey data up to the end of 2012; in 2013 the ITQ survey began a transition to a more lobster-focussed survey.

The survey types (RV, ITQ and Scallop) show the same broad trend of increased lobster catch rate (number per tow) over the last 10-15 years, similar to trends in landings and commercial catch rate. Each survey has strengths and weaknesses in providing data on lobster. The RV survey catch rate is suggested as an interim primary indicator for lobster abundance of LFAs 35-38. The catch rate in the ITQ survey (and its revamped version) is suggested as a primary indicator for lobster abundance for LFA 34. The ITQ survey covered all of the LFA 34 fishing grounds and catch rates were much higher in the nearshore (mean of over 240 lobsters per tow in recent years), compared to the midshore and offshore (8-15 lobsters per tow in the midshore and less than 5 in the offshore). The scallop surveys have high sampling intensity but more limited geographic coverage and a shorter time series. The scallop gear appears to capture smaller lobsters than the other gear types and these surveys could provide a useful secondary indicator of the abundance of juvenile lobsters on scallop grounds.

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