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Why Should We Sometimes Let The Big Ones Go?

Community Based Sustainable Fishing Education Project Information Sheet #2

Download info sheet as a pdf here (recommended). Already read the info sheet? - jump to further reading

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2_2BOFFFF - FAQ, References and additional resources

Further reading:

BOFFFF – the role of large mature female breeders
The importance of Big Old Fat Fecund Female Fish (BOFFFF) is characterised by the allocation of resources during development (Nybakken 1997). Juvenile spend the majority of their resources (stored energy) on increasing their body mass and minimal amounts on gonad growth (Nybakken 1997). Once a fish reaches a certain size (different for each species) there is a switch in the way the resources are allocated and now gonad growth is the priority (Nybakken 1997). The increase in allocated resources allows the gonads to grow much larger and produce eggs of a higher quality to that of smaller fish (Nybakken 1997). Therefore the BOFFFF’s are not only producing more eggs but eggs with a greater chance of survival (Nybakken 1997).

Survival rate of released fish
Davis & Parker (2004) found that the larger the size of the fish increased the chances of survival as long as deep hooked fish had the lines cut. However as these fish inadvertently live in deeper waters it is necessary to consider barotrauma as a cause for post release mortality. Further information on barotrauma and how it can be avoided can be found at write link to Josh’s stuff here!

Reduction in the size at maturity due to fishing pressure and reproductive output
An example of the impact of primarily fishing on spawning aggregations is the North Atlantic cod fishery. This fishery collapsed in the late 80’s and in 1992 the mature breeding stock was only 10 % of the long term average (Trippel, 1995). Trippel (1995) reviews several articles that show a reduction in the age of maturation, which is a sign of overfishing and stock instability. The reduction in age is related to a reduction in the reproductive output of breeding fish (Trippel, 1995). This limits the ability a stock has to recover, especially if fishing continues (Trippel, 1995). This is why it is important that reductions in the age of maturity of South Australian fish stocks (King George Whiting) are identified and adequate measures be put in place.

Marine Protected Areas – protecting BOFFFFs and stock stability
Marine Protected Areas (MPAs) can be effective in protecting BOFFFFs and ensuring stock stability by preventing known spawning aggregations to be targeted by both commercial and recreational fishers (DEH, 2004). Preventing recreational fisherman from targeting spawning grounds is specifically important in preserving King George Whiting. As this is the most recreationally targeted marine finfish species, with recreational catch rates surpassing commercial catch rates (PIRSA, 2007). By protecting spawning sites we can stop situations like the Orange Ruffy and North Atlantic Cod fish stock collapses happening to our own important species.

References:

Davis MW, Parker SJ (2004) Fish Size and Exposure to Air: Potential Effects on Behavioral Impairment and Mortality Rates in Discarded Sablefish. North American Journal of Fisheries Management: Vol. 24, No. 2 pp. 518–524

Nybakken JW, 1997, Marine biology, ecological approach,: Addison Wesley Longman, Inc. Menlo Park, California

DEH, 2004, http://www.environment.sa.gov.au/coasts/pdfs/mpa_blueprint.pdf accessed on the 6th March 2008

PIRSA, 2007, http://www.pir.sa.gov.au/fisheries/recreational_fishing/target_species/king_george_whiting accessed on the 6th March 2008