Distribution and abundance of juvenile Northeast Arctic Greenland halibut (Reinhardtius hippoglossoides) in relation to survey coverage and the physical environment

Comparing survey and assessment data: Consequences for stock evaluation of Northeast Arctic Greenland halibut

“…No age data were available and approximate compositions of age 0-2 were estimated from the length frequencies. These age-groups constituted well-defined modal groups and according to data from Albert et al (2001a) may be approximated by the length groups 0-4 cm, 5-15 cm and 16-25 cm in the first half of the year, and by 0-9 cm, 10-19 cm and 20-28 cm in the second half.…”

“…This index is available on the Internet at <http://www.cgd.ucar.edu/~jhurrell/ nao.html>. Albert et al (2001a) suggested that three mechanisms might be important in linking hydrography to the distribution of juveniles. For an individual year-class each of these mechanisms operates on each of three subsequent years.…”

“…4). The landings of age 3 and 4 were almost exclusively taken within the survey area of scarce south of this area (Albert et al, 2001a) and commercial fishery seldom operate north of this area. Figure 4 shows a series of very low catches of these age-groups from the 1990 year-class onwards.…”

“…It spawns along the slope between Norway and Svalbard (Albert et al, 2001b) and Figure 1 shows the main branches of the Atlantic Ocean current system by which eggs and larvae may be transported. Juveniles are found around Svalbard, but may also occur further away from the spawning grounds (Albert et al, 2001a;Bowering and Nedreaas, 2000).…”

“…Subsequent analyses showed that the disappearance of juveniles was associated with a shift in the distribution of juveniles within the survey area in such a way that the reliability of the tuning data was weakened (Albert et al, 1997). Albert et al (2001a) compared the disappearance of age 1 in the surveys with XSA-results based on catches of the year-classes at older ages and showed that juveniles of the 1989-94 spawning period were distributed outside the survey area to a much higher degree than before. The previously believed weak yearclasses were in fact close to the average and stronger than the preceding ones.…”