Chatham Rise
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Chatham_Rise".

fisheries
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Chatham Rise
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Flemish Cap
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Grand Banks
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Princess Alice
Saya de Malha
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Sea floor map of Zealandia Continent

The Chatham Rise is an area of ocean floor to the east of New Zealand, forming part of the Zealandia continent. It stretches for some 1000 kilometres from near the South Island in the west, to the Chatham Islands in the east. It is New Zealand's most productive and important fishing ground.

Relative to the rest of the Pacific Ocean waters around New Zealand, the Chatham Rise is relatively shallow, no more than 1000 metres deep at any point. This shallowness is made more remarkable by the depth of the ocean immediately to the north and south. To the northeast, the Hikurangi Trench, an extension of the much deeper Kermadec Trench, drops to below 3000 metres close to the New Zealand coast, and further from the coast the Rise borders on the Hikurangi Plateau. To the south, similar depths are achieved in the Bounty Trough. Past the eastern end of the rise, the sea floor drops away to the abyssal plain.

Geology

Geologically and tectonically, the Chatham Rise can be thought of as an extension of the eastern South Island. It was largely dry land around the Cretaceous-Paleogene boundary and formed a large peninsula extending from New Zealand to the Chatham Islands at that time. This was characterized by a volcanic landscape. Fossils found on the Chatham Islands characterize the flora and fauna of the Late Mesozoic Chatham Rise: it had forests dominated by gymnosperms (such as Araucaria, Mataia and Podocarpus) and Lycopodiopsida (clubmosses). Some angiosperms were also present. Dinosaurs such as theropods dwelt on the peninsula and probably evolved into numerous endemic forms.(Stilwell et al. 2006)

Fishing

The Chatham Rise is New Zealand's most productive and important fishing ground. Warm subtropical surface waters from the north and cold subantarctic surface waters from the south meet in the vicinity of the Chatham Rise to create a subtropical front. Nutrient rich waters from the south mix with warm northern waters and create ideal conditions for plankton and the animals that feed on them. The fishing grounds near the subtropical front and particularly the Chatham Rise provide 60 percent of New Zealand’s fish catch. Because the Chatham Rise is relatively shallow, it is accessible to both midwater trawling and bottom trawling. Species include the main hoki, hake, ling, silver warehou, squid, orange roughy and deep sea (oreo) dory fisheries.^[1]

The traditional way to manage fisheries is to focus on a single species - determining how many can be caught without affecting the breeding population and causing harm to the species fishery. However, taking any fish affects the other marine life that eat them, and that in turn affects the marine life that eat the marine life that eat them, and so on up the chain. Scientists from NIWA are working their way through more than 40,000 fish stomachs, to learn about the diets of different species across the Chatham Rise. When these are combined with similar diet studies for sea mammals and birds, and with other climate and ocean studies, there will be a better picture of how different parts of the Chatham Rise ecosystem fit together.^[1]

Notes

1. ^ ^{a b} NZ Ministry of Fisheries: Fisheries and their ecosystems. Retrieved 13 June 2008.

References

• Stilwell, Jeffrey D.; Consoli, Christopher P.; Sutherland, Rupert; Salisbury, Steven; Rich, Thomas H.; Vickers-Rich, Patricia A.; Currie, Philip J.; Wilson, Graeme J. (2006): Dinosaur sanctuary on the Chatham Islands, Southwest Pacific: First record of theropods from the K–T boundary Takatika Grit. Palaeogeography, Palaeoclimatology, Palaeoecology 230(): 243–250. doi:10.1016/j.palaeo.2005.07.017 (HTML abstract)