Fishing impact survey – Firth of Thames/Hauraki Gulf

Samples along a putative gradient of fishing pressure were collected from 18 sites in the Hauraki Gulf. These sites varied in water depth from ~17-35 m and in sediment characteristics from ~1-48% mud and from 3-8.5 ug chlorophyll a/ch3. Variability in macrofauna community composition was attributed to fishing once location and sediment characteristics were taken into account. Purpose: To identify changes in benthic communities at the regional scale that could be attributed to commercial fishing.

Depth, chla, particle size, benthic and epibenthic biota (6 sites in the Waikato Region).

18 sites in Hauraki Gulf/Firth of Thames, including 6 sites that are within the Waikato Region.

Offshore from Colville Bay -

1994

High-resolution side-scan sonar was used to survey the seafloor to identify sites at various locations throughout the Gulf with different environmental conditions and levels of fishing activity. A remotely operated vehicle (ROV) was used to conduct video transects of the seafloor at each site to estimate the density of large epifauna (> 1cm). Macrofauna were sampled from the central area of each site. 5 randomly located grab (muddy sites) or suction-dredge (sandy sites) samples (25 x 25 x 20 cm deep) were collected to assess the density of large macrofauna (> 2mm mesh). Fifteen random cores per site (10cm diam x 12cm) were collected by divers to assess the density of smaller macrofauna (benthos > 0.5mm mesh). Also measured depth, chla, and particle size from surfical samples (0-2 cm deep). Frequency of collection: One off survey

Because of limitations of the sampling gear, not all of the predictions were tested on all of the data. Gaps in collection: grab samples, but not core samples, were collected at sites 7 and 8 due to time/water depth restrictions. Core samples, but not suction-dredge samples, were collected at sites 12 and 18 due to high current velocity. Data quality: Used standard sampling procedures. Attribute accuracy: Not reported Completeness: Not reported

report, electronic, maps, graphs Digital Format: MS Word, MS Excel, statistical plots(?)

Fishing management

See NIWA Sensitivity/Confidentiality: See NIWA

Finished

FRST CO1502 Additional comments: A horse mussel bed was noted in the vicinity of Site 1 (north of Colville Bay). Occasional trawl door tracks were observed in the sediments around Sites 2 and 5 (just outside the restricted trawling and Danish seining area out from Colville. Related information: 1999-2000 Opito trawling survey