Research Document 2024/041
Gaspereau Assessment for the DFO Gulf Region to 2019: Fisheries, Biological Characteristics and Indicators of Status
By Breau, C., and Gibson, A.J.F.
Abstract
This document was prepared in support of the “Assessment of the status of gaspereau stocks of the southern Gulf of St. Lawrence” Regional Advisory Process, April 20-21, 2021. The previous assessment for Alewife (Alosa pseudoharengus) and Blueback Herring (Alosa aestivalis), collectively known as gaspereau, was done in 2001. Stock status in relation to reference points, fishing mortality rates and exploitation rates are available in Gibson and Breau (2024).
This document presents information for Fisheries and Oceans (DFO) Gulf Region up to 2019 on management measures for gaspereau fisheries, commercial gaspereau fisheries landings, gaspereau abundance indices in marine DFO research surveys and, indicators of stock status and biological characteristics for Alewife and Blueback Herring populations in the Margaree River (NS) and the Miramichi River (NB), two rivers in the DFO Gulf Region where these species are monitored.
Alewife and Blueback Herring in individual rivers are considered to be different stocks. The two species have different migration timing and spawning areas and therefore, stock assessments are conducted at river-specific scale and separately for each species.
Catch and effort in commercial fisheries is key for estimating removal rates from populations. No catch and effort information is available for commercial gaspereau fisheries in areas of New Brunswick and Prince Edward Island managed by DFO Gulf Region. In the Gulf Region, reported commercial landings of gaspereau from DFO Statistics Branch have declined over the time series from 1917 to 2019. These are known to be incomplete and may not reflect abundance.
Indicators of stock status for Alewife and Blueback Herring are available for the Margaree River. Catch per unit effort in the Margaree River commercial gaspereau fisheries peaked in the 1980s and has fluctuated around a mean of 61 kg/hour since the last management changes was implemented in 2001.
The commercial gaspereau fisheries in the Miramichi River have not been sampled since 2000. Indicators of stock status for Alewife and Blueback Herring in the Southwest and Northwest Miramichi River were collected from DFO research trapnets upstream of commercial gaspereau fisheries. Catches of both species have declined from 1994 to 2019 on the Southwest Miramichi River whereas catches on the Northwest Miramichi River have been variable.
Commercial gaspereau fisheries are conducted on a large number of rivers in the Gulf Region and systematic sampling of the fisheries catches has only been conducted on one river, the Margaree River. In order to assess the status of gaspereau stocks in the region, additional effort will be required to sample these fisheries, on an intermittent and rotational basis, and the development and validation of other indicators of status such as by examination of age composition and catch curve analyses will be required.
There are very few region-wide indicators of gaspereau abundance. At the regional scale, the bottom-trawl surveys showed a decline in catch rates of gaspereau over time although it is unclear how well the survey indices reflect abundance.
Over the sampling period of 1983 to 2019, the average size of Alewife and Blueback Herring in the Margaree River commercial fisheries declined 41% and 53% by length and 10% and 13% by weight, respectively. A significant declining trend in size-at-age of Alewife and Blueback Herring was observed from 1983 to 2019 on the Margaree River. This was not observed on the Miramichi River but, could be due to the much shorter time series.
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