View source for Chatham Rise

{{Short description|Area of ocean floor to the east of New Zealand}}
{{Use New Zealand English|date=November 2024}}
[[File:Zealandia, topographic map.jpg|thumb|upright=1.35|Topographic map of Zealandia showing the Chatham Rise]]

The '''Chatham Rise''' is an area of ocean floor to the east of [[New Zealand]], forming part of the [[Zealandia (continent)|Zealandia]] continent. It stretches for some {{convert|1000|km|mi}} 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, as well as important habitat for [[whale]]s.<ref>{{Cite web |url=http://www.epa.govt.nz/eez/EEZ000006/EEZ000006_Ngai_Tahu_Marine_Mammal_Cultural_Impact_Assessment_dated_July_2014.pdf |title=Archived copy |access-date=2016-03-14 |archive-url=https://web.archive.org/web/20160202071102/http://www.epa.govt.nz/eez/EEZ000006/EEZ000006_Ngai_Tahu_Marine_Mammal_Cultural_Impact_Assessment_dated_July_2014.pdf |archive-date=2016-02-02 |url-status=dead }}</ref>

Relative to the rest of the [[Pacific Ocean]] waters around New Zealand, the Chatham Rise is relatively shallow, no more than {{convert|1000|m|ft}} 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 Trough]], an extension of the much deeper [[Kermadec Trench]], drops to below {{convert|3000|m|ft|abbr=on}} 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==
[[File:Phosporite-label hg.jpg|thumb|[[Phosphorite]] from the Chatham Rise]]
Geologically and tectonically, the Chatham Rise can be thought of as an extension of the eastern South Island. It was largely dry land at the end of the [[Cretaceous]] (66 million years ago) and formed a large [[peninsula]] extending from New Zealand to the Chatham Islands at that time.

The Cretaceous landscape of the Chatham Rise was characterized by a [[volcanic]] landscape. [[Fossil]]s found on the Chatham Islands characterize the [[flora]] and [[fauna]] of the Chatham Rise in the late [[Mesozoic]]. The region had forests dominated by [[gymnosperm]]s (such as ''[[Araucaria]]'', ''[[Mataia]]'' and ''[[Podocarpus]]'') and [[Lycopodiopsida]] (clubmosses). Some [[angiosperm]]s were also present. [[Dinosaur]]s such as [[theropod]]s dwelt on the peninsula and probably evolved into numerous [[endemism|endemic]] forms (Stilwell ''et al.'' 2006).

==Commercial fishing==
[[File:Ocean circulation near New Zealand.tif|thumb|upright|Subtropical and subantarctic waters meet to form the subtropical front over the Chatham Rise (orange)]]
The Chatham Rise is New Zealand's most productive and important commercial [[Fishery|fishing ground]]. The region is analogous to the North Sea's [[Broad Fourteens]], but is significantly deeper.

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|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% of [[Fishing industry in New Zealand|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 [[Blue grenadier|hoki]], [[Merlucciidae|hake]], [[Pink cusk-eel|ling]], [[silver warehou]], [[squid]], [[orange roughy]] and deep sea (oreo) [[Black oreo|dory]] fisheries.<ref name="ecosystems">NZ Ministry of Fisheries: [http://www.fish.govt.nz/en-nz/Environmental/default.htm ''Fisheries and their ecosystems.''] Retrieved 13 June 2008.</ref>

The traditional approach to [[fisheries management]] has been to focus on a single species – determining how many can be caught before the breeding population is affected to the point of harming the species fishery. There is a current trend towards [[Fisheries management#Ecosystem based fisheries|ecosystem based fisheries]].<ref>University of Liverpool (2006). [https://www.sciencedaily.com/releases/2006/02/060216233254.htm "Marine Ecologists To Help Rebuild Decreasing Fish Stocks"]. ScienceDaily.</ref> Removing any fish affects other [[marine life]] up and down the [[food chain]], such as marine life that eat the fish, and the marine life eating the marine life that eat the fish. Scientists from [[National Institute of Water and Atmospheric Research|NIWA]] are examining over 40,000 fish stomachs to see what different species are eating across the Chatham Rise. These studies, combined with other studies on marine mammals and sea birds and with relevant ocean and climate studies, will show how the different parts fit together in the Chatham Rise ecosystem.<ref name="ecosystems"/>

==Notes==
{{Reflist}}

==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}}

{{Fishing by country}}
{{Oceanic features of Zealandia|state=collapsed}}
{{Authority control}}

{{Coord|-43.7|179.7|dim:1000000|display=title}}

[[Category:Historical geology]]
[[Category:Geography of the New Zealand seabed]]
[[Category:Zealandia]]
[[Category:Pacific Ocean]]
[[Category:Fishing areas of the Pacific Ocean]]
[[Category:Geography of the Chatham Islands]]
[[Category:Fishing in New Zealand]]