Eulachon Migration Study Bottom Trawl Surveys - North

Catch, effort, location (latitude and longitude), and associated biological data from the Eulachon Migration Study Bottom Trawl surveys - North on the coast of British Columbia.

Introduction:
The Eulachon Migration Study Bottom Trawl survey - North (Eul-N) is part of the in the Eulachon Migration Study Bottom Trawl survey series and took place on the coast of British Columbia. The other survey in this series is the Eulachon Migration Study Bottom Trawl survey –South (Eul-S).

The Eulachon Migration Study Bottom Trawl survey - North (Eul-N) was conducted monthly from July 2018 to March 2019 and was funded by the Fisheries and Oceans Canada (DFO) National Rotational Survey Fund.

The objective of this survey was to learn about the distribution, ecology, and migration times of Eulachon into the Nass and Skeena rivers by observing their spatial and temporal occurrence and biological condition over a wide survey region and over several months. This survey follows a random block design in a targeted depth range of 80 – 300 metres. The sampling units were 2 km by 2 km blocks.  

Fishing was conducted using the Canadian Coast Guard Research Vessel Neocaligus to tow an American shrimp trawl net (Cantrawl Nets Ltd., Richmond, BC). The horizontal opening of the polypropylene net was estimated to be 34 to 37 feet (10 to 11 m), while the center of the opening had a vertical height of approximately 7 to 9 feet (2 to 3 m). A 0.4” (10 mm) liner was used in the codend. The net was configured with roller gear and 72” (1.8 m) Thyboron Type 2 trawl doors. Tow duration was typically 5 minutes. The standard hours of fishing were 0800 to 1700 hours, depending on sunrise and sunset in winter months.

The Eulachon Migration Study Bottom Trawl survey – North was conducted by the Department of Fisheries and Oceans Canada (DFO).  This survey fished mainly in Chatham Sound with sets in Hecate Strait and Portland Inlet including Pacific Fishery Management areas (PFMA’s) 3, 4, and 104.

Effort:
This table contains information about the survey trips and fishing events (trawl tows/sets) that are part of this survey series. Trip-level information includes the year the survey took place, a unique trip identifier, the vessel that conducted the survey, and the trip start and end dates (the dates the vessel was away from the dock conducting the survey). Set-level information includes the date, time, location, and depth that fishing took place, as well as information that can be used to calculate fishing effort (duration) and swept area. All successful fishing events are included, regardless of what was caught.

Catch:
This table contains the catch information from successful fishing events. Catches are identified to species or to the lowest taxonomic level possible. Most catches are weighed, but some are too small (“trace” amounts) or too large (e.g. very large Big Skate). The unique trip identifier and set number are included so that catches can be related to the fishing event information (including capture location).

Biology:
This table contains Eulachon biological data including length, sex, and weight. Information is provided on whether stomachs or teeth were examined, and whether genetics (DNA) samples were collected. Eulachon maturity data, diet data, and teeth presence data are available on request from the data contacts. Additional analyses are ongoing, including histology, fatty acid profiling, and genetic analysis; frozen heads are also available for a future aging project. In addition to the Eulachon biological data, lengths and weights were collected from American Shad.The unique trip identifier and set number are included so that samples can be related to the fishing event and catch information.

Organization: Fisheries and Oceans Canada | Pêches et Océans Canada