Shark Depredation and Unwanted Bycatch in Pelagic Longline

Shark Depredation and Unwanted Bycatch in Pelagic Longline Fisheries
A7.5.
Shark Bycatch Composition and Catch Rates
A7.5.1. Catch composition
Blue Sharks were the most common species caught (average 69%
of shark catch, range over time period 63–79%), then Mako Sharks
17% (8–20%) with the remaining 14% (5–29%) being made up of
primarily Bronze Whaler, Cookie Cutter, Crocodile, Dusky, Oceanic
Whitetip, Porbeagle, Thresher, Bigeye Thresher, hammerheads and
Zambezi Sharks (Table A7.2). Blue Sharks were retained in 72% of
cases, released alive in 18% of cases, finned and discarded (dead) in
5% and unknown for the remaining 4%. The discarded animals were
often finned. Observers reported 30% and 25% of Blue Shark catches
were finned in 2000 and 2001, respectively. Mako Sharks were also
frequently caught and most commonly the whole shark was retained
(86%). 10% were released alive and 2% discarded after finning.
Thresher Sharks were infrequently caught and equally discarded/
released and retained. The Bronze Whaler was infrequently
caught, but when it was caught it was usually retained. Crocodile,
Cookie Cutter, Dusky (likely to include misidentified Silky Sharks
(C. falciformis), Oceanic Whitetip, Dog Tooth, Bigeye Thresher,
hammerhead spp. and Porbeagle sharks were infrequently caught,
but almost always discarded/released. Even though the Crocodile
Shark was caught infrequently, there were some occasions when they
were caught in large numbers (e.g. a maximum of 81 was caught in a
single set). The Zambezi Shark was rarely caught and in both cases it
was discarded or released. Observers did not record whether sharks
were hauled onboard dead or alive.
The catch rate of sharks averaged 6.0 sharks per 1000 hooks and
ranged between 4 and 19.8 during 1998-2005 (Table A7.3). Blue
sharks were caught on average at a rate of 4.2 blue sharks per 1000
hooks and Short-fin Makos at a rate of 1.0 per 1000 hooks (1998-2005)
(Table A7.3).
Seasonal differences in catch rates were found for all species
caught in substantial numbers (BlueX 2 = 1026.2, Mako X 2 = 190.8,
Crocodile X 2 = 525.5, Brozne Whaler X 2 = 78.5, Dusky X 2 = 101.5,
Hammerhead X 2 = 54.7, Oceanic Whitetip X 2 = 29.8, Porbeagle X 2 = 105.7,
p