Research Document - 2016/097
Estimation of local spawning biomass of Atlantic Herring from acoustic data collected during fall commercial gillnet fishing activities in the southern Gulf of St. Lawrence (NAFO Div. 4T)
By Surette, T., LeBlanc, C., Claytor, R., and McDermid, J.
Abstract
In partnership with Fisheries and Oceans Canada (DFO), fish harvesters participating in the Atlantic herring (Clupea harengus) fall fishery in NAFO Div. 4T surveyed five spawning grounds in the southern Gulf of St. Lawrence using acoustic sounders over the course of their regular fishing activities from 2002 to 2012. Using a statistical method developed for Fisherman’s Bank, seasonal biomass was estimated for all five spawning grounds. Acoustic data from each area was processed and analyzed to produce nightly biomass estimates for a subset of days over the season. Missing biomass values were simulated using a Bayesian time-series model, then grouped by spawning aggregation using a spatial-temporal clustering model. Seasonal biomass estimates were then produced by year and region. While this approach showed some promise, the model did not provide realistic results for two of the five regions. Furthermore, there are also underlying methodological and biological issues which raise significant doubts as to the comparability of results among regions. Given the inconsistencies in model performance and the underlying issues with the data it was decided that these data could not be used to develop a time series of local abundance indices for herring as part of the fall herring stock assessment. Recommendations are made to aid in future spawning bed specific acoustic surveys.
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