New Zealand Journal of Marine and Freshwater Research abstracts

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Upper-slope fish communities on the Chatham Rise, New Zealand, 1992-99

B. BULL
M. E. LIVINGSTON
R. HURST
N. BAGLEY

National Institute of Water & Atmospheric
 Research Ltd
P. O. Box 14 901, Kilbirnie
Wellington, New Zealand
email: b.bull@niwa.cri.nz

Abstract  Catch rate data for fish species caught in 200-800 m depths during summer trawl surveys of the Chatham Rise to the east of New Zealand in 1992-99 were explored to assess community structure and species associations and to identify changes that occurred within the time series of surveys. The community was dominated by hoki (Macruronus novaezelandiae Hector), a Southern Hemisphere merlucciid hake, which was more abundant than all other species combined and occurred at 97% of the 1048 trawl stations. Three groupings of fish species were identified on the basis of descriptive and cluster analyses, associated with the 200-350, 350-550, and 550-800 m depth ranges. Redundancy analysis showed that depth, latitude, and to a lesser extent longitude explained most of the variation in abundance and composition of catches. Spatial patterns in species diversity and fish density were investigated. Trends within the time series show a significant decline in the biomass of hoki and changes in biomass of several other abundant species. However, there was little change in diversity, density, or division into groupings. The changes in abundance may be related to increased fishing activity and/or other factors such as changes in catchability because of the rising bottom temperatures observed during the surveys.

Keywords  demersal fish community; upper-slope; South Pacific; New Zealand; Chatham Rise; hoki

M00060
Received 3 August 2000; accepted 20 October 2000

PDF file of entire paper: medium quality (2540K); (scanned from paper original: notes about this process)

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