Escape of King Crab, Paralithodes camtschatica. 



From Derelict Pots 



WILLIAM L. HIGH and DONALD D. WORLUND' 



ABSTRACT 



Loss of U)7( per season of pots (traps) in the Alaskan fishery for the king crab, Paralithodes 

 camtschatica. has raised the question of possible loss of crabs and fishes to the derelict, or lost, pots 

 which continue to fish. We conducted a series of experiments during 1974 and 1975 in which tagged 

 king crab were placed in several types of pots and returned to the bottom (soaked) for periods of 1-lfl 

 days. As controls, we released some tagged king crab in Chiniak Bay, Kodiak Island. Alaska. Tagged 

 crab missing from the pots at time of recovery were credited with escape. 



The experiments demonstrated that 'J27f of undersize and 807f of legal-size king crab readily es- 

 caped the derelict pots. Mortality among crab held in pots for various experiments ranged up to 12%. 

 Crab that escaped within 1-4 days were recovered by commercial fishermen at about the same rate as 

 those released in Chiniak Bay near the experiment site. However, those released after a 10- to l(i-day 

 confinement were returned at a much lower rate. Some commercially valuable fishes — such as Pacific 

 halibut, Hippoglossus stenolepis— were also caught in the experimental pots. 



INTRODUCTION 



King crab fishermen in Alaskan waters report losing 

 about 10% of their pots (traps) per season as a result of 

 various mishaps. Lost, or derelict, pots continue to at- 

 tract crabs and other animals for sometime. Animals un- 

 able to escape from derelict pots eventually die. Species 

 most frequently taken with king crab pots include the 

 king crab, genus Paralithodes; the snow (Tanner) crab, 

 genus Chionoecetes; the Pacific halibut, Hippoglossus 

 stenolepis; and the Pacific cod, Gadus macrocephalus. 



As part of an effort to estimate the mortality of crabs 

 and other species in derelict pots, the National Marine 

 Fisheries Service, in cooperation with the Alaska Depart- 

 ment of Fish and Game, conducted several experiments 

 during 1974 and 1975 in Chiniak Bay near Kodiak, 

 Alaska. Our aim was to learn more about the signifi- 

 cance of derelict pots on the king crab resource. Specif- 

 ically, we wished to determine: 1) the rate of escape of 

 undersize and legal-size king crab from four types of 

 pots; 2) the effect of crowding upon escape; 3) the effect 

 of baited pots and the presence of dead crab upon escape 

 rate; and 4) the effects of confinement on subsequent 

 recapture of tagged king crab. 



We did not simultaneously conduct independent tests 

 to determine entry rates of crab into king crab pots. How- 

 ever, crab entry would not be critical if our study were to 

 show that all those entering would eventually escape. 



If destruction of animals was found to be significant, 

 then it would be appropriate to equip king crab pots with 

 a degradable panel, that is, a portion of the enclosure 

 which would deteriorate rapidly and finally disintegrate 

 when left in the sea unattended. Degradable panels 



(featuring web, secured by natural fibers) are already a 

 standard part of sablefish, Anoplopoma fimbria, traps 

 (Hipkins 1974) and have been proposed for king crab 

 pots." However, the cost in time to fishermen to maintain 

 degradable panels is significant; therefore, they should 

 not be required unless the benefits justify the expense. 



HISTORY OF THE PROBLEM 



Although some king crab fishing by U.S. fishermen 

 began just before the Second World War (1941-45), it was 

 not until nearly 1960 that the fishery was well estab- 

 lished. The peak catch of 159.2 million pounds by about 

 300 vessels was reached in 1966. Fishing effort has con- 

 tinued to be high since 1965, but the catch has declined 

 and was only 97.8 million pounds in 1975 (Rod Kaiser^). 



Concern for the possible detrimental effects of derelict 

 pots has been expressed in several qufulers. Crab fisher- 

 men reported occasionally retrieving lost pots contain- 

 ing numerous crabs which they believed would die and 

 attract other crabs, repeating the cycle until the trap was 

 destroyed. Both crab and halibut fishermen observed 

 that halibut often enter baited pots and are quickly at- 

 tacked and killed by sand fleas (amphipods), ending up 

 as bait within the pot for at least a short time. 



Scientists studying gear operations expressed concern 

 because available evidence suggested that heavy steel- 

 framed pots with synthetic enclosure webbing would re- 

 main intact for some years. Occasionally, during 

 research cruises, derelict pots were recovered which had 

 apparently been submerged for 1 or more years. They 



'Northwest and Alaska Fisheries Center. National Marine Fisheries 

 Service, NOAA, 2725 Montlake Boulevard East, Seattle, WA 98112. 



=In 1976, the Alaska Board of Fisheries directed that after 1 July 1978, a 

 degradable panel be placed in all king crab pots. 1976 Alaska Commer- 

 cial Fishing Regulations. 1976-77 ed., p. 42. 



'Rod Kaiser. Alaska Department of Fish and Game, Kodiak, AK 99615, 

 pers. commun.. September 1976. 



