methodology - Forest and Bird

D Uncertain/
unknown yield or
stock size
E Stock below 20%
Bo
E Stock below Bmsy
and subject to
other factors
Status and sustainability are unknown due to lack of adequate
monitoring data or research. There are no estimates of yield
i.e. MCY, CAY or risk based yields or forward projections.
Fisheries operating under such uncertainty are not adopting a
precautionary approach and cannot be shown to be
sustainable.
Fishery is over-fished and catches need to be substantially
reduced to allow the stock to recover eg orange roughy.
Fishery is over-fished and likely below the size that would
support the MSY and is subject to either recent low
recruitment which would prevent recovery to Bmsy within 10
year, serial depletion (e.g. paua) or recent serious disease
events (eg dredge oysters).
Note: MSY in this context includes MCY, CAY, or to achieve the agreed stock target level.
5.2 Fishing method – bycatch and habitat damage
Fishing is the most pervasive direct impact on the marine environment down to depths of 1200 metres or
more (Jennings and Kaiser 1998, Hall 1999). The impacts of fishing has a wider footprint than the localised
impacts of land originated sedimentation and includes the loss of biodiversity (Cryer et al.,., 2002; Hiddink
et al.,., 2006; Koslow & Gowlett-Holmes, 1998; Koslow, 2001; Probert et al.,., 1997; Thrush et al.,., 2001;
Thrush & Dayton, 2002).
The direct effects of fishing include the impact on:
Non-target species, including bycatch of fish, invertebrates (eg coral and sponges), marine mammals,
seabirds and turtles (Abraham & Thompson, 2009; Abraham et al.,., 2010; Baird 2001, 2004a, b, c,
2005a, b, c, d, e; Cryer et al.,., 2002; Manly et al.,., 2002a,b,c,). Bycatch can be retained, turned into
meal and oil for sale, or discarded. (Discarding QMS species is not allowed unless prior permission is
gained).
Habitat, for example, where fishing gear can damage and remove seabed (benthic) plants and animals
such as sensitive sponges, corals, bryozoans (lace corals), and shellfish, which are important settlement
surfaces, cover and habitat for other organisms (Cranfield et al.,., 1999; Cranfield et al.,., 2001;
Cranfield et al.,., 2003; Cranfield et al.,., 2004; Norse & Watling, 1999; Thrush et al.,., 1998 & 2001;
Thrush & Dayton, 2002). Trawling and dredging also can disturb sediment which can smother
organisms and block light for algae and seaweeds in shallow water (Committee on Ecosystem Effects of
Fishing 2002; Kaiser, 2000; Kaiser et al., 2001; Kaiser et al.,., 2006).
The indirect effects of fishing are more difficult to assess and measure. These potential changes include
alterations to food chains and predator-prey relationships (Jennings and Kaiser 1998 and Symes 1998).
Examples of indirect effects include:
Removal of key/dominant herbivores and carnivores such as snapper, rock lobster, sharks, and paua
leading to changes in community structure and a potential reduction in biodiversity or other species
(eg, jellyfish or kina) which are less targeted and which may increase beyond their natural stable range;
The removal of abundant species such as pilchards may impact on natural predators including penguins
and other protected or globally threatened seabirds;
Discarding of unwanted catch may result in changes in food webs and community structure, increasing
the abundance of scavengers. It can also attract protected or threatened seabirds, sea lions and seals
which are then caught by fishing gear.
Forest & Bird Best Fish Guide 2012 – 2013: Criteria for Ecological Rankings 12