Assessment of the East Greenland-Iceland fin whale population using a four-area model

• Main Authors: Branch, Trevor A, Butterworth, Doug S
• Format: Report
• Language: English
• Published: International Whaling Commission 2006
• Subjects: East Greenland-Iceland fin whale; fin whale population; four-area model; Greenland; East Greenland; Fin whale; Iceland
• Online Access: http://hdl.handle.net/11427/17586; https://open.uct.ac.za/bitstream/11427/17586/1/Branch_Assessment_East_2006.pdf

The East Greenland-Iceland (EGI) fin whale population is modeled as four subpopulations with movement between the following areas: East Greenland (area 1), West Iceland (area 2), East Iceland (area 3) and the Far East (area 4). The model is sex- and age-structured, and is fitted to CPUE, sightings survey abundance, and mark-recapture data using both maximum likelihood and Bayesian approaches. Movement parameters are not differentiated by sex since the inclusion of sex-specific movement parameters did not improve the AIC. For the base case assessment scenario, best fits to the data were obtained when West Iceland and East Iceland are effectively fully mixed with a low level of interchange with East Greenland and little interchange with the Far East region. For the base case and all sensitivity tests, the overall recruited population is increasing and above 74% (base case 84%) of pre-exploitation abundance (K), and subpopulations in all areas are above 68% (base case 78%) of the individual K values. MSYR for the recruited population is 0.020 for the base case and 0.014 to 0.036 for the sensitivity tests. Projections for annual catches of 0, 100, and 200 whales taken from West Iceland indicate that only the last would result in abundance decreases compared to current levels. Under catch levels of 200 whales the probability of the total EGI population falling below 60% of pre-exploitation levels within the next 30 years was 5.7%, 7.3% and 11.5% for the 1+, recruited and mature components of the population, although there was a 51% probability of this occurring for the West Iceland mature component.