Fisheries and Oceans Canada (DFO) conducts an annual summer multidisciplinary scientific survey with a bottom trawl in the Estuary and the northern Gulf of St. Lawrence since 1984. Over the years, this survey has been conducted on four vessels: the MV Lady Hammond (1984-1990), the CCGS Alfred Needler (1990-2005), the CCGS Teleost (2004-2021) and the CCGS Cabot (2022-current). It is important to note that the objectives, the methods used and the identification of the species during these surveys have improved over time in response to DFO requests and mandates. The data are therefore not directly comparable between these surveys. 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. Monitor the pelagic ecosystem

5. Collect samples for various research projects

Survey description

The survey covers the northern Gulf of St. Lawrence, that is the divisions 4R, 4S and the northern part of division 4T 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 Lady Hammond is a bottom trawl Western IIA. 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 sub-sample. 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 redfish 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 biological and 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 ).