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Fishery Bulletin 100(4) 



depth range of species will influence their susceptibility 

 to capture: a higher proportion of a species' population 

 is likely to be taken if there is an overlap. Species with 

 a broader depth range may have a spatial refuge from 

 trawling, making them less susceptible. The depth range 

 of species was determined from previous research surveys 

 in the NPF and from the literature. 



Axis 2: The capacity of a species to recover once 

 the population is depleted 



There were five criteria (probability of breeding, maximum 

 size, removal rate, annual fecundity, mortality index I on 

 this axis. 



Probability of breeding We assumed that a species is 

 likely to have a greater capacity to recover from a de- 

 crease in population due to trawling if most individuals 

 are captured after they have bred. The probability that 

 an individual of a species had bred before capture was 

 determined from the mean length at capture in relation 

 to the species' recorded size at maturity. The mean length 

 at capture of a species was recorded in the research and 

 observer surveys 1996-98 (Table 1). Size at maturity was 

 determined from the available literature and from our 

 estimates outhned previously. 



A t-test (Sokal and Rohlf 1996) was used to determine 

 whether the mean length at capture was significantly dif- 

 ferent from the size at maturity for each species. 



