Reproductive potential and maturity staging of Greenland Halibut (Reinhardtius hippoglossoides, Walbaum)

Abstract

Greenland halibut (Reinhardtius hippoglossoides, Walbaum) is a commercially important fish species in the Barents Sea. This fishery has been strongly regulated, including a fishing ban from 1992 to 2009. Studies of fish reproduction are needed to extend the knowledge about this species in order to improve management and to avoid another decay of the stock. This Master Thesis describes the relationships between fecundity (thousands oocytes per female) and length (cm) ("Fecundity=2 ×" 〖"10" 〗^"-6" " × " 〖"Length" 〗^"3.9418" ) and fecundity (thousands oocytes per female) and weight (g) (Fecundity=0.003 × Weigth^1.1251) for Northeast Arctic Greenland halibut based on 138 females taken in November-December 2011 on the continental slope of the Barents Sea. Fecundity was compared to previous data from the same area and it was found to be in the same range as data from 1996, 1997 and 1998. Maturity stages were stated using the new scale proposed by Kennedy et al. (2011) based on oocyte diameter measurements. These data were compared with the maturity stages given at sea, using both a standard macroscopic scale and the macroscopic scale special for Greenland halibut. Differences were found, both with regard to stating of maturity stages and the boundary between mature and immature individuals. Spawning stock size and total egg production were calculated using both methods, and an overestimation of the spawning stock size, as well as of the total egg production, was found when the macroscopic scale was used. Due to the fact that it is difficult to implement the microscopic scale at sea, it is proposed that when using the special macroscopic scale for Greenland halibut females, the boundary of immature females is moved from stage 1 to also include stage 2.