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Research Document - 2013/040

Recent spring offshore acoustic survey results for capelin, Mallotus villosus, in NAFO Division 3L

By: Frances K. Mowbray

Abstract

The spring NAFO Division 3L acoustic survey for capelin provides indices of biomass and abundance of 2J3KL capelin, in addition to information on capelin distribution, biology and behavior. Spring capelin acoustic surveys have been conducted annually in 1982-92, 1996, 1999-2005 and 2006-12. The biomass of capelin found during the survey has changed dramatically within this time series, peaking at 7 million tonnes in the late 1980s, dropping an order of magnitude in the early 1990s and again in 2010 to an all-time low of 23,000 t. However during the last two years the survey biomass has rebounded to levels more consistent with those of the late 2000s (206,000–210,000 t). Coincident with these changes in biomass have been shifts in the spatial distribution of capelin, initially to the north and toward the shelf break, though returning in 2011 and 2012 to spatial distributions more reminiscent of those seen during the 1980s. On-going changes have occurred in capelin vertical distribution with capelin distributed in areas with deeper water, in closer proximity to the bottom and exhibiting decreased diel vertical migration. Age composition and size structure have also changed over time with the current index comprised of mainly ages 2 and 3 fish, while ages up to 5 were present historically. The age at maturation has also decreased with approximately 10 times more age 2 fish maturing, a trend which continues over the last 2 years.

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