Enhancing catch value from matauranga Maori-based fish potting methodologies

Abstract

Negative impacts on the marine environment due to commercial fishing provide incentive for the development of environmentally sound fishing methods. Instead of trawling, the Maori-owned Waikawa Fishing Company (WFC) seeks to use unbaited fish pots; a low impact method with reduced bird and mammal bycatch, and reduced fuel use. Prior research demonstrated only 20% of catch values from WFC’s Z pot design achieved the required $35 break-even catch value identified by prior study. In order to increase catch values to an economic level, this study generated information and recommendations around pot design and potting methodology, which was provided to the WFC, to enhance the matauranga (traditional knowledge) that design and methodology decisions are based on. A six- week field trial tested variations of pot design, mesh type, region, soak time and collapsibility. The amount of variation caused by methodology indicated economically viable catch values can be achieved using the existing Z design, in contrast to an initial focus on design changes as the solution. Economically viable catch values from Z pots increased from 20% (in prior research) to 33% in the present study, indicating methodological improvement; this is likely to continue as WFC’s potting experience increases. The Z pots (mean $28.54) caught higher values than a new S pot design (mean $11.77). Increased catches of higher value large fish in Z pots was possibly due to funnel design; an avenue for further research. Standard mesh was the best economic option, although undersized fish bycatch in all three mesh types indicates further research is required to develop an environmentally appropriate mesh type or escape gaps. Region had a large effect on catch value; standard mesh Z pots at Cape Campbell (mean $33.59) produced higher values than Cape Jackson ( mean $9.05). Catch values increased with soak time; four day soaks gave higher catch values (mean $33.38, $0.35/hr), but one day soaks gave higher hourly catches (mean $13.45, $0.56/hr); fuel usage will determine the optimal soak time. Collapsibility had no effect on catch value; a useful factor for increased capacity for small boats. In-situ video of behavioural responses to pot entrance design indicated minor behavioural differences influence catch rates. The probability of fish entering the Z entrance (P=0.09) was higher than the S (P= 0.04), and increased with the amount of time spent around the pot. 1.5% of fish approaches resulted in capture, highlighting the passive mechanism of potting, and indicates huge potential for increased catch values with design modification. Video demonstrated variation in the habitat-scale location (i.e. distance from reef) of pot deployments. Given the variation in field trial catch values within each region, habitat-scale location is potentially an important factor of catch value. The percentage of catch values reaching the break-even point can be achieved with refined methodology, particularly regional and habitat-scale location choices. WFC’s Z pot is suitable for economically viable commercial fish potting; design modification is not immediately required, but is an avenue for increases to catch value once methodological parameters are optimised.