Silver Hake of Scotian Shelf: Fishery, Environmental Conditions, Distribution, and Biology and Abundance Dynamics

Abstract

The results of USSR/Russian scientific research on silver hake (Merluccius bilinearis) population on the Scotian Shelf (NAFO Div. 4VWX) with regard to environmental conditions, distribution, biology and abundance dynamics are summarized for the period from the early-1960s to 1997. A brief description of the fishery is provided. Silver hake of the area form a self-reproducing group, geographically separated from more southwesterly stocks. They distribute demersally for the most part of the year and form aggregations mainly in deep-water depressions of the shelf and warm slope waters. Silver hake may be classified as a species with a high rate of renewal and of pronounced abundance fluctuations in response to climatic variations. The effect of any stock-recruitment relationship is over-shadowed by the impact of oceanographic factors within a wide range of spawning biomass. This paper makes an attempt to predict the trends of abundance of the silver hake population in the late-1990s and the first decade of the next century. While sharp variations of year-class abundance are caused by environmental variability, it is suggested that during this period, favourable conditions are expected for formation of relatively strong year-classes and, therefore, for good fishing.

Response of Scotian Shelf silver hake (Merluccius bilinearis) to environmental variability

“…These results are in agreement with Rikhter et al. () who argued that bottom temperature was central in modulating the distribution of silver hake with food availability playing a secondary role. Indeed, both of these drivers may be characterized by zooplankton PC1 as this principal component exhibited a strong correlation (Pearson's correlation coefficient = 0.77; Figure S2) with physical PC1, which is broadly associated with warming in the region (i.e., warmer surface and bottom waters, as well as less ice and a smaller CIL volume).…”

“…These results are in agreement with Rikhter et al. () who noted that density‐dependent effects on Scotian Shelf silver hake can be suppressed by physical conditions such that recruitment cannot be predicted based on spawning stock biomass, and oceanographic conditions must also be considered.…”

“…Although adult biomass [−1] did not feature in the optimal model, as may be expected given its previously established with recruitment (Rikhter et al, 2001), it did appear in four of the top five models, suggesting an important role in driving recruitment. All three terms in the optimal GAM had a similar form comprising linear and plateaued regions.…”

“…Rikhter et al. () suggested that unfavorable temperature conditions may delay spawning and decrease survival of young fish. In addition to physical processes, numerous phenology variables contributed to peaks in recruitment.…”

“…Consistent with silver hake preference for warmer conditions (Sigaev, 1994), recruitment was consistently shown to increase when bottom-water temperatures increased and the CIL declined in volume. Rikhter et al (2001) suggested that unfavorable temperature conditions may delay spawning and decrease survival of young fish. In addition to physical processes, numerous phenology variables contributed to peaks in recruitment.…”