Multidisciplinary winter survey for assessing groundfish in the northern Gulf of St. Lawrence (MV Gadus Atlantica 1978 - 1994)

Fisheries and Oceans Canada (DFO) conducted a winter multidisciplinary scientific surveys with a bottom trawl the northern Gulf of St. Lawrence and Cabot Straight from 1978 to 1994. The specificities of the missions onboard the MV Lady Hammond are described below.

Objectives:

1. Assess groundfish populations abundance and condition
2. Assess environmental conditions
3. Conduct a biodiversity inventory of benthic and demersal megafauna
4. Collect samples for various research projects

Survey description

This winter survey covers the northern Gulf of St. Lawrence, that is the divisions 4R, 4S and 3Pn of the Northwest Atlantic Fisheries Organization (NAFO). A stratified random sampling strategy is used for this survey and the fishing gear used on the MV Gadus Atlantica is an Engel 145 Otter trawl. Standard trawling tows last 30 minutes, starting from the time the trawl touches the sea floor. Towing speed is 3.5 knots.

Data

For each fishing tow, the catch is sorted and weighed by taxa; individuals are counted and biological data are collected on a subsample. For fish, crab and squid, size and weight are measured by individual and, for some species, sex, gonad maturity, and the weight of certain organs (stomach, liver, gonads) are also evaluated. The soft rays of the anal fin are counted for redfish and otoliths are collected for Greenland halibut and Atlantic cod. Invertebrates are weighted and counted (no individual measurements).

The biological data are divided into 4 files: a “Metadata” file containing set information, a “Catches” file containing catches per set for fish taxa, a “Carbio” file containing morphometric measurements per individual and a “Freql” file containing the length frequency of fish.

It's important to note that this is raw data. Only sets considered successful are retained. In each set, all species are kept, with a few exceptions. For more information please contact the data management team (gddaiss-dmsaisb@dfo-mpo.gc.ca).