Scientific Observer Sampling Manual ... - Kimdietrich.com

Each of these user groups has different information needs. For instance, stock assessment
modelers may require total catch estimates by species (weight and numbers), length-weight
or length-age relationships of catch and size at maturity (to determine breeding grounds and
timing, recruitment) depending on the model used.
1.4 Global fisheries – Gear, Issues & Management Instruments
1.4.1 Commercial fishing gear
Commercial fishing gear can be categorize as either passive whereby fish move to the gear
(e.g., longline, traps, gillnet) or active where gear moves to the fish (e.g., trawl, purse seine).
There are more than 60 gear types classified by the International Standard Statistical
Classification of Fishing Gear and these are grouped into 11 categories (Appendix 6);
however, the majority of global catch is taken by five gear types: purse seine, mid-water
trawl, bottom trawl, gillnet and hook and line (based on 1950-2001 data; Watson et al. 2006).
In general, purse seine nets catch fish by surrounding fish from all sides as well as
underneath. Both mid-water and bottom trawl nets are towed nets consisting of a wide
opening with wings that herd fish into a cone-shaped body and are collected in the terminal
end or codend. Gillnets consist of a wall of nearly invisible net in which fish become gilled or
entangled. Hook and line gear consists of natural or artificial bait placed on a hook fixed to
the end of a line. Hook and line gear can be configured with a single hook up to tens of
thousands of hooks (Nedelec and Prado 1990, FAO 2005-2009).
1.4.2 Issues
The primary issues constraining global marine capture fisheries in the last decade and facing
fisheries in the future include:
1. Illegal, Unreported and Unregulated (IUU) fishing constitutes a serious threat to: (i)
fisheries, especially those of high-value that are already overfished (e.g. cod, tuna, redfish
and swordfish); (ii) marine habitats, including vulnerable marine ecosystems; and (iii)
food security and the economies of developing countries (FAO 2009b). IUU is considered
an environmental crime involving theft of resources. There is an international initiative in
progress to implement binding port state measures. IUU is discussed in more detail in
Chapter 13;
2. Bycatch and discards can have significant consequences for populations, food webs and
ecosystems. The most recent estimate of annual global discards was 7.3 million tons
(1992-2001; (Kelleher 2005)). Several international initiatives (e.g., the development of
International Plans of Action or IPOAs) focused on reducing the catch of specific
taxonomic groups have been successful in raising awareness of the issue and reducing
global catch. Bycatch reduction devices (BRDs) are discussed further in Chapters 6-7;
3. Overfishing and overcapacity of fishing fleets (Beddington et al. 2007);
4. Trade and trade subsidies as they relate to overfishing and overcapacity; and
5. Climate change impacts on fish distribution and the frequency of extreme weather
events.
1-3