Annual Lobster and Rock Crab Trawl Surveys at Magdalen Islands

Fisheries and Oceans Canada conducts annual trawl surveys for American lobster and rock crab populations around the Magdalen Islands. The survey, running since 1995, covers up to 48 stations each September, with data on cephalothorax length, sex, shell stage, and crab counts. The dataset comprises four linked files containing station information, individual lobster measurements, crab counts, and crab measurements.

Use Cases

• Analyze population abundance trends for American lobster using annual station and measurement data linked by date, st, and tr columns.
• Model the relationship between lobster cephalothorax length and shell stage or sex across different survey stations.
• Assess rock crab population structure by examining shell width, sex, and shell condition measurements from predetermined stations.
• Study the spatial distribution of catches by linking station location data with lobster and crab count files.

Strengths

• Annual time series provides longitudinal data from 1995 to the present.
• Standardized methodology with tows covering 500 meters and a trawl opening averaging 10 meters.
• Data is split into four logically separated files (stations, lobster measurements, crab counts, crab measurements) that can be linked.

Limitations

• Data quality is noted as unverified, consisting of raw data.
• Rock crab individual measurements are only collected at predetermined stations or when time permits, potentially creating incomplete records.
• Survey duration and station coverage (max 48 stations) can be limited by weather conditions each year.

Provenance

Source

Fisheries and Oceans Canada

Collection Method

Annual benthic trawl surveys using a modified Nephrops trawl deployed from the CCGS Leim, with organisms sorted and measured aboard.

Time Range

1995 to present (annual surveys in September)

Freshness

Updated annually; last update recorded in March 2026.

Geography

Southern part of the Magdalen Islands, Canada, from Baie de Plaisance to Grande-Entrée.