Thread: Aus Day 2014 - WA off to a bad start... Shark cull

Originally Posted by beagleONE

Gentlemen, unfortunately I can not gain full access to the document I was after
I did gain access to a PhD Thesis, which I got the following information from.

I was able to gain some insight which shows that two different hook types were trialed, one being the traditional 'j hook' and the other being a 'circle hook' (circles back towards the shank more than a 'j hook').

Mortality rates upon collection generally dropped amongst most species of shark when using the circle hooks. Although there were two extremities of 100% mortality on circle hook catches, and 100% survival on circle hook catches. These were two separate species.



Here are some direct quotes from the thesis.

All potentially aggressive sharks caught alive were accommodated in a water-filled, wooden tank which was assembled on the deck of R/V Sinuelo, and transported towards the continental slope in order to remove them away from the area of risk. The distance and duration of the transport depended on the size and health of the shark, and some primary vital signs such as the contraction periodicity of gill openings and the maintenance of body equilibrium were continuously monitored to assure that the shark was released in good condition.

A total of 22 tiger sharks comprising 11 males and 11 females and measuring between 90 and 295 cm in total length (TL) were tagged and released off Recife, representing a total of 15 acoustic transmitter deployments and 16 PSAT-tag deployments (Table 7.1). Most sharks were released in good health conditions except for three sharks which did not respond when released and thus had to be assisted by one person in the water, who balanced them at the sea surface and pushed them upstream until they demonstrated an autonomous swimming capacity. Also, two other sharks could not easily maintain their biological position underwater by releasing time (i.e., they tended to turn with their ventral-side up) and so they were kept in the hook next to the boat until they exhibited enough strength to be released (Table 7.1).

After being transported away from shore and released, most tiger sharks reacted well and actively moved away from the boat. Notably, many specimens stayed visibly at the surface in slow swimming for a considerable time, as long as five minutes, before diving out of sight. One specimen first headed towards land but suddenly inverted its direction, ~20 m further, and returned to the boat always at the surface, eventually diving to pass under the boat in the direction of open sea.





These 22 tiger sharks were tracked between June 2008 - Sept 2011. Of the twenty two; seventeen recorded good overall health, three reported fair health and two reported poor health...






UNIVERSIDADE do ALGARVE Faculdade de Ciências e Tecnologia
Bioecology and movement patterns of sharks off Recife, Brazil: applications in the mitigation of shark attack hazard
André Sucena Afonso

So 5 out of 22 were worse off after being caught, I guess they lasted 3 yrs after being relocated.


Thanks for posting up what you could find.


Cheers Ean

I recon as I am in Broome at the moment that he should leave the crocs and get rid of the problem peope