Many marine top-predators, among them many shark species, are particularly vulnerable to environmental changes as they are contingent on the various prey species along the food chain and their responses to shifts. The porbeagle (Lamna nasus) is a large pelagic shark that inhabits cold-temperate regions of the oceans on both hemispheres. During the last century, it was heavily targeted by fisheries. Today, the Northeast Atlantic subpopulation is considered critically endangered by the IUCN, but there is still little known about the status of porbeagle in many areas of its distribution range.
Victor Gonzáles Triginer addressed in his Masters thesis entitled ” Distribution range, occurrence and bycatch risk of a large pelagic shark, the porbeagle (Lamna nasus), in Norwegian waters” the distribution range and abundance of porbeagles in Norwegian waters. Analyses of catch data from fisheries from the past decades revealed (i) the presence of porbeagle all year round in Norwegian waters, (ii) a decreasing trend in landings of porbeagle, consistent with the implementation of zero catch regulations, (iii) a catch peak in the summer months, and (iv) two potential hotspots in the Norwegian Sea for being fished. Bycatch through nets was identified as the main threat for fishery mortality for porbeagle in Norwegian waters. The thesis provided important information for developing and implementing sustainable strategies for an efficient management of the Northeast Atlantic porbeagle subpopulation.
The figure in the teaser for this day showed the total weight of porbeagle landed in Norway per year from 1977 to 2019. The blue line corresponds to a linear regression with confidence intervals of 95%; slope of -1.397 and p-value < 0.001.
Victors Masters thesis was conducted as a cooperation between the Institute of Marine Research, Tromsø, and the FEZ group with Dr. Claudia Junge and Lutz as supervisors.
Text in the teaser: Would like to know what is decreasing in weight so constantly? The door on December 11th will reveal it.
Picture in the teaser: