'Trawl' database - fisheries. Ministry for Primary Industries.

Purpose to describe fish species and assemblage patterns, and to monitor fish stocks for changes in their abundance (biomass) and population size frequency compositions.Surveys have been undertaken by the Kaharoa since 1982 (East Coast) and 1986 (West Coast) at fixed stations using stratified random trawls. The project objectives are to determine the relative abundance and distribution of inshore finfish species, and to estimate biological parameters for stock assessment.

Contains 692 stations within the Hauraki Gulf Region and ? stations along the West Coast. Target species have been snapper, John dory, and red gurnard; with recent surveys targetting 1 year old snapper (in the Hauraki Gulf only?). Biological data collected an analysed includes age/length frequency, length-weight, and reproductive condition.

New Zealand wide

Trawls undertaken at randomly selected positions – from northeast of Bream Head (Whangarei Harbour) to Great Mercury Island; and ….. west coast?

Hauraki Gulf – 1984-90, 1992, 1996, 1997 (voyage codes KAH8203, KAH8517, KAH8609, KAH8613, KAH9711, KAH8716, KAH8810, KAH8917, KAH9016, KAH 9212 and KAH9720). Differs from Kendrick & Francis (2002) – RV Kaharoa: 1982, 1984-90, 1992-94, 1997. ??????? West Coast -

Methods from early surveys: trawl surveys are conducted from R.V.Kaharoa within depth and area strata based on previous catch rates. The surveys use a two-phase stratified random design (after Francis 1984). A high-opening bottom trawl with cut away lower wings and a 30 - 40 mm codend mesh was used. All trawls were carried out during daylight hours (0500 – 1700 hours NZST), with a towing speed between 3-3.5 knots in a direction that maintained the same water depth (~10m). Distance towed was constant at 0.7 nautical mile (1296m) for shallower stations and 1 nautical mile (1852m) for deeper stations. The catch weight of each trawl is measured to the nearest 0.1 kg. A percentage of all commercially important fish and squid species were sampled from each trawl. Measurements include length, sex, reproductive stage, length-weight for a range of sizes. Otoliths were also collected. Environmental conditions were recorded including sea surface temperature, air temperature, bottom temperature, wind direction and speed, cloud cover, bottom type and contour, barametric pressure, sea condition and colour, and swell height and direction. Frequency of collection: Kaharoa surveys were restricted to spring (Sept-Dec) and Autumn (April-June). More recent surveys see Ministry for Primary Industries Trawl Survey (NABIS)

larger fish (such as snapper over 35 cm) are able to out-swim the sampling gears, and many probably escape. Kaharoa stations were concentrated in the inner Hauraki Gulf. Fish species were identified by reliable researchers.

reports, electronic Digital Format: relational database

Determining optimum sustainable yields Determining the roles of species in their ecosystems

See Ministry for Primary Industries Sensitivity/Confidentiality: See Ministry of Fisheries

Updated (every one-two years ?).

Additional comments: A strong correlation exists between the average sea surface temperature in February of the preceding summer, and the number of 1+ snapper the following summer (until the most recent survey in 2000, the correlation coefficient was 0.96). Another similar dataset exists for the RV Ikatere. Surveys were undertaken in 1964, 1965, 1968, 1969, 1971, 1973, 1975-80. Ikatere surveys spanned much of the year and stations were distributed relatively evenly throughout the Hauraki Gulf. Trawling equipment dimensions however varied from that used by the Kaharoa.