The New Zealand Best Fish Guide - SEAFOOD Ecolabelling: Principles and Practice - page 373

Table 18.1 Definitions used in New Zealand fisheries management.

MCY - maximum constant yield is the maximum constant catch that is sustainable with an
'acceptable level of risk' at probable levels of future biomass for a fish stock.
CAY - current annual yield is the estimate of the maximum sustainable catch for the current year
in reference to a level of fishing mortality which has an 'acceptable level of risk'.
MAY - maximum average yield - which is the long-term CAY and equivalent to MSY.
Bo - the unfished, initial or virgin recruited biomass for a stock.
B MSY - the recruited biomass that supports the maximum sustainable yield.
B MAY - the recruited biomass that will support the maximum average yield.
B MCY - the recruited biomass that supports the MCY.
MSY - maximum sustainable yield, in relation to any stock, means the greatest yield that can be
achieved over time while maintaining the stock's productive capacity, with regard to the
population dynamics of the stock and any environmental factors that influence the stock
(section 2, Fisheries Act 1996).

Impacts of fishing method
The direct effects of fishing techniques considered included the impact on:

non-target species, including bycatch of fish, invertebrates (such as corals and
sponges) (e.g. Cryer et al . 2002); and

habitat - fishing gear can damage and remove seabed (benthic) plants and an-
imals such as sensitive sponges, corals, bryozoans (lace corals) and shellfish,
which are important settlement surfaces, cover and habitat for other organisms
(e.g. Cranfield et al . 1999, 2001).

Active fishing methods such as dredging and trawling generally have a greater
impact on the seafloor than passive techniques such as longlining and gillnetting.
The degree of impact caused by various techniques varies with depth, type of
seafloor, weight and type of gear used (Collie et al . 2000). The scale of impact can
be substantial. For example, a single trawler making three trawl tows of 6 h each,
using bottom trawl gear with 100 m between the doors, at an average of three knots,
would trawl the bottom over an area of about 10 km 2 in one day (Cryer et al . 2002).
Each species reviewed in the Forest and Bird assessment may be caught by
a number of fishing methods, but for each species there is usually a dominant
technique. For instance, hoki is caught mainly by trawling. The fishing techniques
scored for each species in the assessment is the most common fishing methods used
to commercially catch the species in New Zealand. If there was a range of methods
used, the fishery was assessed on the basis of the method with the most significant
impact.
Forest and Bird reviewed the results of Morgan and Chuenpagdee's study (2003)
to determine whether there were effects that were different in the New Zealand
fisheries and considered the comparative impacts of different methods. Forest and