Fisheries and Oceans Canada (DFO) conducts an annual multidisciplinary scientific survey with a bottom trawl in the Estuary and the northern Gulf of St. Lawrence since 1978. Over the years this survey has been conducted on four vessels: the MV Gadus Atlantica (1978-1994), the MV Lady Hammond (1984-1990), the CCGS Alfred Needler (1990-2005) and the CCGS Teleost (2004-2021). 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 CCGS Alfred Needler are described below.

Objectives:

1. Assess groundfish and northern shrimp population abundance and condition

2. Assess environmental conditions

3. Inventory species biodiversity

4. Monitor the pelagic ecosystem

5. Inventory marine mammals populations

6. Inventory seabirds populations

7. Collect samples for various research projects

Survey description

The survey covers the divisions 4R, 4S, 3Pn and the northern part of division 4T of the Northwest Atlantic Fisheries Organization (NAFO). This survey follows a stratified random sampling design and the fishing gear used on the CCGS Alfred Needler is a URI shrimp trawl (81'/114'). Standard trawling tows last 25 minutes, starting from the time the trawl touched the sea floor. Towing speed is 3 knots.

Data

For each fishing tow, the catch is sorted and weighed by taxa; biological data are then

collected on a subsample. For fish, crab and squid, size and weight are gathered 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 the otoliths are collected for several species such as witch flounder, Atlantic cod, Greenland halibut and Atlantic halibut. A roughly 2-kg shrimp sample is sorted and weighed by species (and by stage of maturity for northern shrimp). The shrimps are measured individually. The other invertebrates are counted (no individual measurements) and photographed.

The catches per tow for fish taxa are available below. This data is also available via the 'Biodiversity' application on the St. Lawrence Global Observatory (SLGO). For more information please contact the data management team (gddaiss-dmsaisb@dfo-mpo.gc.ca ).