Boje: Intermingling and seasonal migrations of Reinhardtius htppoglossoides 



415 



grounds to eastern Greenland and probably as 

 far as southwestern Greenland (Sigurdsson'; 

 Boje^). In 1959, Smidt (1969) observed the re- 

 capture west of Iceland of Greenland halibut 

 that had been tagged in Licthenau Fjord in 

 southwestern Greenland in 1954. Riget and 

 Boje (1989) noted the recapture west of Iceland 

 in 1980 of Greenland halibut that had been 

 tagged in Godthaab Fjord in 1964. 



In the present study, tagging experiments in 

 the ^ords of eastern and western Greenland 

 from 1986 to 1998 are evaluated to determine 

 the stock discreteness of Greenland halibut 

 populations in the Northwest Atlantic and 

 to describe seasonal migrations of Greenland 

 halibut within inshore areas. 



Materials and methods 



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Greenland halibut from four areas around 

 Greenland were tagged between 1986 and 

 1998. The tagging was carried out in the 

 fjords of eastern Greenland at Ammassalik in 

 September 1990, in the ^ords of southwestern 

 Greenland from Cape Farewell to Godthaab 

 Fjord in January 1987-88, in the Qords of 

 northwestern Greenland from Disko Bay to 

 Upernavik during July-August 1986-98, 

 and off western Greenland from Davis Strait 

 to Baffin Bay during May-August 1991-93 

 (Table 1, Fig. 1). Samples were collected with 

 longlines (Mustad Autoline Systems) from 

 research vessels fishing at depths between 400 

 and 900 m — a range that is standard for the 

 commercial fishery (Boje^). Fishing time for each set was 

 approximately six hours. 



A landing net was placed under each fish from the time 

 it left the water until the fish was landed onboard the ship 

 to avoid damage from the hook (i.e. the gravitational drag 

 of the hook while the specimen was removed from the wa- 

 ter). The hook was removed with care and only fish hooked 

 in the mouth region were selected for tagging because 

 these injuries were generally not fatal. Condition of the 

 fish was judged visually, mainly by examining the color 

 of the gills and by assessing internal hooking injuries. 

 Length of the fish was measured to the nearest full cen- 

 timeter (total length) and fish larger than 35 cm were se- 

 lected to increase the possibility of immediate recapture in 

 the fishery. Each fish was tagged in the musculature with 



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Boje, J. 1997. Larval growth and spawning of Greenland 

 halibut in West Greenland waters and the possible influences 

 by hydrographic conditions. ICES (International Council 

 for the Exploration of the Sea) international symposium on 

 "Recruitment dynamics of exploited marine populations: physi- 

 cal-biological interactions," Baltimore 22-24 Sept. 1997. ICES, 

 Palaegade 2-4, DK-1261 Copenhagen K, Denmark. 

 Boje, J. 1989. The fishery for Greenland halibut in Subarea 

 1. NAFO (Northwest Atlantic Fisheries Organization) SCR 

 Doc. 89/27, sen N1603, 8 p. 



Figure 1 



Map of release sites (shaded areas). NAFO (Northwest Atlantic Fisheries 

 Organization) (0-2) and ICES (International Council for the Exploration of 

 the Sea) (V-XIV) divisions are indicated. 



a yellow T-bar tag (Floy T-bar anchor tags, FD-68B yellow) 

 just below the dorsal fin ray near the head. Immediately 

 after having been tagged, the fish was released. 



For an evaluation of migratory routes, the numbers of 

 recaptured fish were adjusted for fishing activities (an- 

 nual landings) in recapture area (i.e. NAFO/ICES divi- 

 sion) for the year of recapture and these numbers were 

 expressed as the number of halibut per 100 metric tons 

 of annual landings in the recapture division. Landing sta- 

 tistics were obtained from Greenland Statistical Office, 

 NAFO Statistical Bulletin 1986-93, NAFO STATLANT 

 21A data and ICES Cooperative Research Reports of the 

 ACFM 1986-98. 



To analyze seasonal movements among "resident" 

 Greenland halibut (i.e. fish caught less than 100 km 

 from the release site) of northwestern Greenland, the 

 §ords were stratified into five rectangles of equal area, 

 and positioned in an east-west direction. A random-walk 

 model (Skellam, 1951) was applied to the distribution of 

 all releases (/i=4319) pooled for the entire period, 1986- 

 98, for all five areas, assuming equal probability that the 

 fish would migrate either east or west or remain in the 

 area (P=0.33). The model operated on a time unit of three 

 months, thereby allowing each fish to move from only one 

 rectangle to the next rectangle within a quarter of a year. 



