Age and size selectivity of the Gaspereau River Alewife Fishery: Implications for the assessment of this stock
LE3 .A278 2017
Bachelor of Science
Biological reference points are metrics based on the biological characteristics of a fish stock and its fishery. They provide the link between stock assessment and management objectives, and are used to gauge whether management objectives are being achieved. Age and size can influence the impacts of a specific harvest rate depending on whether younger, smaller or o lder, larger fish are being harvested. A fishery that is selective for certain age classes w ould have different biological reference point s for the stock, and could require different management of the fishery. In this study, I examined the selectivity of a commercial alewife fishery on the Gaspereau River, Nova Scotia. Alewife ( Alosa pseudoharengus ) is a diadromous, herring - like fish species that spawn in the rivers and lakes along the eastern seaboard of North America. Alewife are fished throughout their range as they return to their natal rivers to spawn. In s pring 2016, biological characteristics , including weight, fork length, sex, and age data were collected from alewife sampled at a commercial fisher’s stand, and at a fish ladder 4 km upriver. Data were used to reconstruct numbers - at - age for the total run. S ignificant difference s w ere found in mean fork length, weight, age, and proportion of repeat spawners between the two sampling locations, indicating that the fishery is highly selective. Selectivity was calculated for age classes three through s ix , incorporated into the calculations for the b iological reference points for this fishery, and compared to existing b iological reference points based on the assumption the fisher y is non - selective. Although this study shows the fishery is selective, effects on the biological reference points were minor, likely due to the absence of immature fish in the
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