The New Zealand Best Fish Guide - SEAFOOD Ecolabelling: Principles and Practice - page 375

was also revised to reflect that in the New Zealand zone, this method is not known
to capture dolphins and other marine mammals.
Scores vary according to the overall impact, the amount of bycatch (non-target
catch which is either utilised or discarded) and effect on habitat, ranging from mini-
mal impact to substantial damage (see Table 18.3). For example, pelagic longlining
for tuna and snapper causes negligible damage to the seafloor but still receives a
low score because the technique kills large numbers of seabirds and other bycatch
(including sharks), which are generally discarded.

Biology and risk of overfishing

The life span, age at sexual maturity, fecundity (number of eggs or young pro-
duced), productivity and level of natural mortality are all factors that determine
the susceptibility of a species to the effects of fishing, including how quickly it
will recover from overfishing. In addition, the geographic distribution, degree of
endemism (whether it is restricted to one area or widely distributed), behaviour
and social structure of a species (whether it is solitary, territorial, highly migra-
tory or site specific) also contribute to how a species responds to commercial
exploitation.
Fish species may be classified according to any of the criteria with an intrinsic
rate of increase being the key factor (Musick et al . 2001). The species was assessed
according to the lowest productivity parameter in Table 18.4 for which data are
available. For example, a species with high fecundity ( 10 4 ), but late maturity >

(5-10 years) and long life span ( > 30 years), would be classified under the very low

productivity category.
In addition to the categories developed by Musick and others for the American
Fisheries Society (Musick et al . 2000, 2001), a new category for species with very
high resilience has been added to give a five-point risk rating for each species
and to make the range for scores for these criteria consistent with other criteria
(Table 18.4).
In addition to the productivity risk to a stock, there are a number of other factors
to consider:
rarity;
small range and whether the species is endemic to New Zealand;
specialised habitat requirements such as kelp forests;
population decline, including size and speed of decline; and
loss of habitat, especially on species with a small range and specialised habitat
requirements.

The biology of each species is scored from A to E - from most resilient to fishing,
to least resilient based on lifespan, natural mortality, time to maturity, reproductive
output and productivity.