571 



Abstract — We evaluated light-based 

 geulucation estimates from pop-up sat- 

 ellite tags in high latitudes because 

 some of the largest fisheries in the 

 world are in areas where this tech- 

 nique has not been assessed. Daily 

 longitude and latitude were estimated 

 by using two Wildlife Computers soft- 

 ware programs: 1) Argos Message 

 Processor (AMP), which summarizes 

 light intensity data transmitted to 

 satellites, and 2) Time Series Proces- 

 sor (TSP), which uses more detailed 

 data obtained from retrieved tags. 

 Three experiments were conducted 

 in the northern Gulf of Alaska using 

 tags placed on 1) Pacific halibut in 

 outdoor aquaria, 21 a fixed mooring 

 line at various depths and 31 wild 

 Pacific halibut. TSP performed better 

 than AMP because the percentage of 

 days with geolocation estimates was 

 greater and the mean error magni- 

 tude and bias were smaller for TSP 

 and increased with depth for both 

 programs: however, latitude errors 

 were much greater than longitude 

 errors at all depths. Light-based 

 geolocation enabled us to discern 

 basin-scale movements and showed 

 that the Pacific halibut in our study 

 remained within the Gulf of Alaska. 

 We conclude that this technique pro- 

 vides a feasible method for inferring 

 large-scale population structure for 

 demersal fishes in high latitudes. 



Evaluating light-based geolocation 



for estimating demersal fish movements 



in high latitudes 



Andrew C. Seitz (contact author) 



U S G S, Alaska Science Center 

 1011 E. Tudor Rd, MS 701 

 Anchorage, Alaska 99503 



and 



University of Alaska Fairbanks 



Institute ol Marine Science 



PO Box 757220 



Fairbanks, Alaska 99775-7220 



E-mail address; aseltz@ims.uaf.edu 



Brenda L. Norcross 



University of Alaska Fairbanks 

 Institute of Marine Science 

 PO Box 757220 

 Fairbanks, Alaska 99775-7220 



Derek Wilson 



Jennifer L. Nielsen 



U S G.S. Biological Resources Division 

 Alaska Science Center 

 1011 E Tudor Rd, MS 701 

 Anchorage, Alaska 99503 



Manuscript submitted 24 August 2005 

 to the Scientific Editor's Office. 



Manuscript approved for publication 



20 December 200.5 by the Scientific Editor 



Fish. Bull. 104:571-578120061. 



Demersal fishes at high latitudes 

 support some of the most lucrative 

 fisheries in the world. An example 

 is the Pacific halibut {Hippoglossus 

 stenolepis) fishery off Canada and the 

 United States. Currently, the Inter- 

 national Pacific Halibut Commission 

 (IPHC) manages the Pacific halibut 

 population as a single, panmictic stock 

 from northern California through the 

 eastern Bering Sea based on genetic 

 (Grant et al., 1984; Bentzen et al., 

 1998) and tagging data (Skud, 1977). 

 However, Pacific halibut movements 

 and population structure are not fully 

 understood and mixing may be more 

 restricted than assumed, as evidenced 

 by a number of local depletions in 

 recent years (Hare'). A method for 

 estimating movements over large dis- 

 tances is needed to improve the ability 

 to identify populations and manage 

 the harvest. Population structure and 

 movement information is needed for 

 management of several other high- 



latitude fisheries including Atlantic 

 halibut (Hippoglossus hippoglossus). 

 Pacific cod (Gadus macrocephalus) 

 and Greenland turbot (Reinhardtius 

 hippoglossoides) (God0 and Haug, 

 1988; Shimada and Kimura, 1994; 

 Albert, 2002). 



New methods using information col- 

 lected by electronic tags, which con- 

 tain miniaturized onboard computers, 

 are providing location estimates of 

 demersal marine fishes (see review in 

 Arnold and Dewar, 2001). One such 

 method, the tidal location method, 

 has been used to geolocate North Sea 

 plaice (Pleuronectes platessa) (Hunter 

 et al., 2003). This method compares 

 the tidal range and time of high 



Hare, S. R. 2005. Investigation of the 

 role of fishing in the Area 4C CPUE 

 decline. Int. Pac. Halibut Comm. Report 

 of Assessment and Research Activities 

 2004:185-198. Int. Pac. Halibut. Comm, 

 PO Box 95009, Seattle, WA 98145- 

 2009. 



