Science Response 2013/010

Update to 2012 on spawner abundance and biological characteristics for striped bass (Morone saxatilis) in the southern Gulf of St. Lawrence

Context

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) first assessed the Striped Bass population of the southern Gulf of St. Lawrence (southern Gulf) in 2004. The COSEWIC concluded that southern Gulf Striped Bass comprised a single Designatable Unit (DU) and assessed it as ‘Threatened’ mostly because of a single spawning location and small area of occupancy (COSEWIC 2004). In 2006, a Recovery Potential Assessment proposed recovery objectives for the population, and in 2011, an Allowable Harm Assessment reviewed threats to the population (DFO 2006, 2011). In 2012, the recommendation to not list this population under the Species at Risk Act was published in Part 1 of the Canada Gazette (Canada Gazette 2012). The status of Striped Bass was reviewed in 2011 to support the COSEWIC’s re-assessment of the species (Douglas and Chaput 2011a, 2011b). The COSEWIC affirmed that the population in the southern Gulf was a single DU and assessed it as ‘Special concern’, a lower risk category than previously and largely a consequence of the increased spawner abundance in recent years (COSEWIC 2012).

The increased abundance of Striped Bass in the southern Gulf has resulted in requests by aboriginal groups and the recreational angling community to re-open fisheries. In consideration of potentially new management options for the future, DFO Ecosystems and Fisheries Management has requested an update on the abundance of the southern Gulf Striped Bass spawning stock and biological characteristics to 2012.

This science response report is the result of the Science Special Response Process of February 14, 2013 and provides an update of the Striped Bass spawner abundance in the Northwest Miramichi estuary for the 2011 and 2012 spawning seasons. The estimated spawner abundance in the Northwest Miramichi in 2011 was 203,100 fish (median value, 2.5 to 97.5 percentile range of 90,080 to 438,400) and enough to meet the population’s recovery objective for the first time since 1993. While no spawner abundance estimate could be derived for 2012 due to an early spawning period that preceded the assessment activity, the recovery objective was considered to have been met for the second time. As the abundance of Striped Bass has increased, those with fork lengths greater than 60 cm and older than five years of age have also increased but remain a small proportion of the spawning population. Relative to the length metric in the Maritimes Fisheries General Regulations, a total length of 68 cm is equivalent to a fork length of 62 cm.

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