New Zealand Journal of Marine and Freshwater Research abstracts
Fate of discards from deep water crustacean trawl fishery
off the south coast of Portugal
MARGARIDA CASTRO
ARTUR ARAÚJO
PEDRO MONTEIRO
CCMAR Universidade do Algarve
8005-139 Faro, Portugal
email: mcastro@ualg.pt
Abstract Abstract Trawling for crustaceans takes place on
the south coast of Portugal at depths between 200
and 800 m. Large amounts of discards are released
back to sea, reaching the bottom in the general area
where trawling occurs. The objective of this work
was to study the time taken for decomposition of the
discards, to identify the most important scavenging
species involved, and to evaluate the impact on the
species targeted by the fishery. We conducted a series
of 22 trials, using traps baited with samples of
the discards. The time of immersion varied between
1 and 40 h. The amount of tissue removed from the
discards was evaluated on a qualitative scale of 1–3,
and quantitatively. The species caught in the traps
were identified. Considerable consumption of the
bait had occurred after 5 h of immersion. After 24 h
of immersion only fish bones were left; past 40 h,
consumption was complete. The conger eel (Conger
conger) was the most common fish species present
in the traps. Two species, the amphipod Scopelocheirus
hopei and the isopod Natatolana (Cirolana)
borealis, were identified as most important for the
recycling of organic matter in the system. The stomach
contents of a sample of species caught in trawls
were analysed for the presence of small scavengers.
Preliminary results show that S. hopei and N. (C.)
borealis are part of the diet of some of the target
species of this fishery, such as the Norway lobster,
Nephrops norvegicus and the rose shrimp
Parapenaeus longirostris.
Keywords fate of discards; food subsidies; impact
of trawling
M04030; Online publication date 31 May 2005 Received 9 February 2004; accepted
26 April 2005
New Zealand Journal of Marine and Freshwater Research, 2005, Vol. 39:
437-446
0028-8330/05/3902-0437© The Royal Society of New Zealand 2005
PDF file of entire paper: Print-quality (211K) |
screen-quality (141K)
This year's abstracts |
Journal home page |
All abstracts |
Publishing home page
