Unlike many other shark species, blue sharks are relatively productive and may attain high abundances locally. This is reflected in the fisheries catch composition which the researchers monitored in the local area where blue sharks constituted 81.5% of the total catch in terms of number of individuals caught.
Blue shark composition varies with sea surface temperature (SST), time of year and lunar cycle. The highest catch rate of blue sharks in the Central North Atlantic occurred during the winter months whilst the summer months yielded the lowest catch rate. This is congruent with evidence that female blue sharks migrate in the warmer months and appear off the coasts of Ireland and SW England. The highest catch abundance of blue sharks also coincided with the coolest SSTs, with the highest catch rate occurring in waters of 17.5°C and the lowest at the higher SST of 23°C. Evidence of several life stages of the blue shark in the Central North Atlantic indicates that this is an important ecological area for blue shark populations from both sides of the North Atlantic, as well as being a nursery area for blue sharks.
Owing to the over exploitation of many shark species by the fisheries industry, in depth knowledge of population structure and composition of shark species is an important tool in assessing vulnerability of each species. The blue shark is the most frequently caught pelagic shark species by the fisheries industry, with an estimated 86,000 tonnes fished per year; in recent years the swordfish fisheries have begun to target blue sharks owing to a reduction in the swordfish catch in the region.
Vandeperre, F., Aires-da-Silva, A., Santos, M., Ferreira, R., Bolten, A. B., Serrao Santos, R. and Afonso, P. (2014) Demography and ecology of blue shark (Prionace glauca) in the central North Atlantic. Fisheries Research. 153, 89-102
