Abstract.- Mortality due to re- 

 tention of lobsters in derelict traps 

 was evaluated over a 2-year period 

 using two approaches. First, a string 

 of eight empty, single-chamber, plas- 

 tic traps was deployed at 40 m depth 

 off Oahu, Hawaii, and monitored 

 periodically by scuba during a 6- 

 month period in 1990. The traps 

 were stable and remained intact 

 despite adverse oceanic conditions. 

 Numerous entries and exits of lob- 

 sters were recorded. For the second 

 test, the ability of lobsters to exit 

 traps was tested in a series of field 

 and laboratory trials of trap strings 

 stocked with Hawaiian spiny lobster 

 Panulirus marginatus and slipper 

 lobster Scyllarides squammosus. 

 The number of lobsters that died in 

 stocked traps was less than 4% of the 

 test population and differed signifi- 

 cantly from zero only in the labora- 

 tory evaluation (x" 5.42, P 0.02). 

 The two species exited similarly; 

 however, the pattern of exits in lab- 

 oratory and field tests differed sig- 

 nificantly (x- 23.889, P0.03). All 

 lobsters exited within 56 days in a 

 pattern generally approximating an 

 exponential decline. Our evidence 

 suggests that little direct mortality 

 of lobsters is due to the inability to 

 exit traps, and consequently ghost 

 fishing by these traps is not con- 

 sidered a problem for spiny and slip- 

 per lobsters. 



Evaluation of ghost fishing 

 in the Hawaiian lobster fishery 



Frank A. Parrish 

 Thomas K. Kazama 



Honolulu Laboratory, Southwest Fisheries Science Center 

 National Marine Fisheries Service. NOAA 

 2570 Dole Street, Honolulu Hawaii 96822-2396 



Manuscript accepted 14 August 1992. 

 Fishery Bulletin, U.S. 90:720-725 (1992). 



Continued fishing by lost traps has 

 become the focus of increasing con- 

 cern by both fishery managers and 

 scientists. The recent trend for trap 

 fisheries to replace their degradable 

 traps with designs made from more 

 persistent synthetic materials has 

 heightened the seriousness of pos- 

 sible ghost fishing by such unrecov- 

 ered traps. Ghost fishing has been 

 defined as the continued fishing of 

 irretrievable gear (Smolowitz 1978). 

 Such a definition fails to distinguish 

 between permanent entrapment and 

 temporary occupation of a trap (e.g., 

 for feeding or shelter). Mortality oc- 

 curring in abandoned traps should be 

 measured to assess the impact of 

 ghost fishing on a particular fishery. 

 The phenomenon of ghost fishing 

 has been observed in a wide range of 

 trap fisheries with diverse trap 

 designs (e.g.. High 1976, Pecci et al. 

 1978, Smolowitz 1978, Paul 1983). 

 Despite this attention, few studies 

 have effectively assessed the ghost 

 fishing problem for any species. The 

 more rigorous evaluations rely on 

 continued underwater field observa- 

 tions of simulated lost traps (Breen 

 1990). With this method, mortalities 

 have been clearly demonstrated in 

 temperate fisheries in which animals 

 were unable to exit traps fitted with 

 nonreturn entrance devices. Features 

 such as spring-loaded doors and slick 

 plastic entrance chutes effectively 

 reduce the ability of some animals to 

 exit actual and simulated lost traps, 

 resulting in reported mortalities of 

 26-55% (High 1976, Miller 1977, 

 Breen 1987). Conventional wooden, 



two-chamber or "parlor-type" traps 

 designed for the American lobster 

 Homarus americanus have produced 

 mortalities of 12-25% (Sheldon and 

 Dow 1975, Pecci et al. 1978, Smolo- 

 witz 1978). 



Ghost fishing poses a potential risk 

 to at least some trap fisheries, and 

 such a risk requires assessment for 

 each species and trap configuration. 

 Tropical lobsters have been largely 

 neglected in the controlled evaluation 

 of mortality by ghost traps. Isolated 

 anecdotal reports of tropical lobsters 

 found in lost traps (Sutherland et al. 

 1983) and tank studies made to date 

 (Paul 1983) do little to predict realis- 

 tic, long-term effects of lobsters in- 

 teracting with modern traps in the 

 field. 



Hawaii's lobster fishery targets 

 two species, Hawaiian spiny lobster 

 Panulirus marginatus and slipper 

 lobster Scyllarides squaiyirnosus. A 

 laboratory study by Paul (1983) used 

 California parlor-type traps made of 

 wire to determine the effectiveness 

 of escape vents in releasing under- 

 sized Hawaiian spiny lobster. Paul 

 (1983) suggested that ghost fishing 

 might occur in these traps and rec- 

 ommended that the Hawaiian fishery 

 consider incorporating degradable 

 escape panels to facilitate the escape 

 of adult lobsters. By 1985 the fishery 

 had adopted a more cost-effective 

 molded-plastic trap design as the 

 standard gear. Degradable panels 

 have not been included. 



In 1989 the Hawaiian lobster indus- 

 try reported that more than 1 million 

 traps were set in the Northwestern 



720 



