Sharks are vulnerable to overfishing because of their low reproductive rates and often low growth rates. Tuna longline fisheries, which operate mainly in oceanic waters beyond the continental shelves that surround land masses, catch many pelagic (open-ocean) sharks, including shortfin mako sharks (Isurus oxyrinchus). Most pelagic sharks fall near the middle of the shark productivity scale, and there is concern that catching too many of them could lead to population depletion. In New Zealand waters, mako sharks are the second most commonly caught shark species (after blue sharks) on tuna longlines. They are not targeted but are taken as bycatch.
NIWA is in its third year of a 5-year phased project on the deepwater line fishery in Tonga funded by the NZ Aid Programme’s Partnership for International Development Fund. The aim of the project is to deliver the improved governance, management, and economic and biological sustainability of the fishery focusing on deepwater snapper and bluenose in the Tonga EEZ.
We don’t clearly understand the ecological effects of commerical toothfish fishing in the Ross Sea region. To improve our knowledge, we conducted a survey of demersal (bottom-dwelling) fish species on the Ross Sea slope - particularly grenadiers and icefish - during the 2015 Antarctic Ecosystems Voyage.
The Ross Sea lies 3500 km south of New Zealand next to Antarctica. It encompasses the main fishing grounds for Antarctic toothfish, a species NIWA scientists are studying so that it can be fished sustainably.
Rig shark is an important inshore commercial fish species in New Zealand, and we need to understand more about their habitats, movements, nursery grounds and vulnerability to human impacts to ensure they are managed sustainably and their productivity is enhanced.
The main aim of the surveys is to estimate the abundance of hoki and other commercially important species (such as hake and ling), but during the 20 consecutive surveys NIWA scientists have also been able to study other aspects of deepwater biodiversity on the Chatham Rise, including fish distribution, abundance, and ecology.
We need information on the food web structures of our marine ecosystems in order to manage the effects on the ecosystem of fishing, aquaculture and mining, as well as understanding the potential impacts of climate variability and change on our oceans.
A primary aim of the Sultanate of Oman Ministry of Fisheries Wealth is to ensure that fisheries are developed and managed for the advantage of the people of Oman in a manner that is sustainable and maintains biodiversity.