Snapper are the most important recreational fish species in New Zealand and are often released back to the sea after capture.
Little is known about the survival of fish after they are released.
NIWA conducted a study using volunteer fishers to catch 960 snapper at different depths and with different hook placements.
The captured snapper were kept in holding nets and monitored by NIWA divers over several days.
Fish hooked in the lip had a low chance of dying if caught at shallow depths, but the chance of dying increased as depth increased.
Fish hooked elsewhere on the body had a higher chance of dying, with those hooked deep in the gut having the highest chance of dying.
This study suggests that fishing practices can impact fish survival, but there are ways to potentially reduce post-release mortality.
Understanding how fishing affects fish survival is therefore an important consideration for catch and release fisheries and when setting catch limit regulations.
Published
Last updated
ISBN Online
978-1-991285-24-9
ISSN Online
1179-5352
National Chemical Contaminants Programme – Raw Milk Results Summary (July 2014 to June 2015)
This National Chemical Contaminants Programme (NCCP) – Raw Milk Result Summary July 2014 to June 2015 provides a summary of results for raw milk and colostrum sampled over the full 2014/2015 dairy season, spanning the period 1 July 2014 to 30 June 2015
Published
Last updated
National Chemical Contaminants Programme – Raw Milk Results Summary (July 2013 to June 2014)
This National Chemical Contaminants Programme (NCCP) – Raw Milk Result Summary July 2013 to June 2014 provides a summary of results for raw milk and colostrum sampled over the full 2013/14 dairy season, spanning the period July 2013 to June 2014
Published
Last updated
Dairy National Chemical Contaminants Programme – Raw Milk Results Summary (July 2011 to June 2012)
This Dairy National Chemical Contaminants Programme (NCCP) Report provides a summary of results for the full 2011/12 dairy season, spanning the period July 2011 to June 2012
Published
Last updated
National Chemical Contaminants Programme – Raw Milk Results Summary (July 2012 to June 2013)
This Dairy National Chemical Contaminants Programme (NCCP) Report provides a summary of results for the full 2012/13 dairy season, spanning the period July 2012 to June 2013
Published
Last updated
FAR 2024/16 Catches and size and age structure of the 2021–22 hoki fishery and a summary of input data used for the 2023 stock assessment
This report updates and summarises the commercial catches, standardised catch per unit effort (CPUE), and observer and research data for hoki (Macruronus novaezelandiae) caught commercially during the 2021–22 fishing year.
These data include time series of length-at-age and catch-at-age from observer and land-based sampling of commercial catch. Length and age data from spawning and non-spawning fisheries are compared with those from previous years.
The overall catch in the 2021–22 fishing year was lower than the catch in 2020–21. Catches in 2021–22 decreased in most areas (west coast South Island, Cook Strait, Chatham Rise, Sub-Antarctic, and east coast North Island) and increased in the east coast South Island and Puysegur fisheries. The CPUE indices varied by area but were all at or above the long-term average.
Catch-at-age data are important for the assessment of fish stocks because they provide information on the year class strength of age classes caught and are used in analyses of trawl surveys and commercial fisheries. Most of the catch in 2021–22 was of fish 45–90 cm length from the 2006–2019 year classes.
The 2014 and 2015 year classes were important in all areas except for the Chatham Rise, and the 2016 and 2017 year classes were low in all the main fisheries. The 2018 and 2019 year classes appeared strong in the WC.north, SA.snares, SA.auck, CR.shallow, and CR.deep sub-fisheries.
Biomass indices from research surveys and results from other research on hoki in the most recent year are also briefly described. Data in this report were incorporated in the model for the hoki stock assessment in 2023.
This report presents the results from the 16th inshore trawl survey in a time series started in 1992 along the west coast of the South Island, from Farewell Spit to the Haast River mouth, and in Tasman Bay and Golden Bay.
The survey covers depths from 20 to 400 m (core strata) and surveys many species but is mainly focused on giant stargazer, red cod, red gurnard, spiny dogfish, and tarakihi. Since 2017, two additional strata have been surveyed in 10–20 m in Tasman Bay and Golden Bay to cover the full distribution of snapper in the geographic area.
Data collected include length, weight, and maturity data for selected species, and collection of otoliths (fish ear stones) of the key species for ageing. The trawl survey provides time series of relative biomass estimates and age, length, and maturity stage information used for stock assessments and fisheries management advice for key inshore species.
In 2023, 58 phase one stations were successfully completed in the core strata and another six were carried out in strata 20 and 21. Four phase two stations were completed to reduce the coefficient of variation for spiny dogfish and snapper.
Biomass estimates (in tonnes) for the target species in the core strata were: giant stargazer, 915 t; red gurnard, 1498 t; red cod, 69 t; snapper, 3633 t; spiny dogfish, 3043 t; and tarakihi, 493 t.
The snapper biomass (core strata plus the 10–20 m strata) was the highest ever in the time series and nearly triple that from the previous survey in 2021, with most fish 20 years or younger. Juvenile snapper were caught mostly in the 10–20 m strata. These strata provide important information on future recruitment and contain a variable proportion of the adult population.
A catchability analysis of the survey indicates that the survey can be considered representative of the time series.
Published
Last updated
ISBN Online
1179-5352
ISSN Online
978-1-991120-81-6
FAR 2024/03 Relative abundance, size and age structure, and stock status of blue cod in Foveaux Strait in 2023
South Island recreational blue cod fisheries are monitored by Fisheries New Zealand using potting surveys to assess the status of the stocks. The results of the Foveaux Strait surveys are important inputs for full quantitative stock assessments conducted for BCO 5 every five years.
This report describes the results of the random-site blue cod (Parapercis colias) potting survey carried out in Foveaux Strait in February 2023—as well as for three previous surveys (2010, 2014, and 2018). Estimates are provided for population abundance, size structure from fish length, and age structure from otoliths (ear bones collected for ageing), as well as population sex ratio, total mortality, and fishing mortality.
The overall weighted mean length of blue cod in 2023 was 32.0 cm for males and 28.5 cm for females, and mean age was 5.9 years (1–11 years) for males and 6.2 years for females (1–16 years). There were no clear age class modes in 2023 and little evidence of spawning activity during the survey.
The scaled length frequency distributions and mean length of all blue cod were similar for all four surveys, although, in 2023, the proportion of small males was less than in previous years.
Survey abundance (total blue cod mean catch rate) from the four surveys significantly increased between 2010 and 2014, with no change in 2018, followed by a significant decline of 57% in 2023.
The proportion of pots with no catch was similar for the first three surveys (25 to 32%), but in 2023 this increased to 49%. There were no trends in sex ratio over the time series which was around 50% male.
The age structure was similar among the four surveys with most fish between 4 and 8 years of age and relatively few fish over 10 years, particularly males. The fishing pressure is concentrated on just a few older cohorts, some of which are poorly represented.
Relative to the target reference fishing mortality of F=0.15 for blue cod, the estimated mortality in 2023 was nearly seven times higher, indicating that overfishing is occurring. Fishing mortality was also considerably higher than the target for all three previous surveys.
Report - Aquatic Environment and Biodiversity (AEBR)
Subjects
News & Resources, Publications
Rig nursery grounds were defined and ranked from a review of existing information and a nationwide set net survey of 14 major harbours and estuaries in 2011. Kaipara and Raglan harbours were very important nurseries, followed by Waitemata, Tamaki and Porirua harbours. South Island harbours do not appear to be important rig nurseries. Juvenile snapper and grey mullet were frequent bycatch in North Island estuaries, and were most abundant in the same harbours as rig.
Published
Last updated
ISBN Online
978-0-478-38877-0
ISSN Online
1179-6480
AEBR 096 A Review of the Marine Soft-Sediment Assemblages of New Zealand
Report - Aquatic Environment and Biodiversity (AEBR)
Subjects
Fisheries, News & Resources, Publications
This review of existing information describes the current state of knowledge on soft-sediment marine assemblages around New Zealand; it identifies hotspots of biodiversity; highlights threats to, and the vulnerability of, assemblages; discusses knowledge gaps; and recommends areas or assemblages that could be the subject of directed future research. The review is supported by The Marine Soft Sediment Biodiversity Bibliographic Database which houses over 700 references.
Published
Last updated
ISBN Online
978-0-478-38878-7
ISSN Online
1179-6480
AEBR 097 Chatham-Challenger Ocean Survey 20/20 Post Voyage analyses: Objective 9 – Patterns in Species Composition
Report - Aquatic Environment and Biodiversity (AEBR)
Subjects
News & Resources, Publications
This report describes relationships, patterns and contrasts in benthic species composition, assemblages and habitats, both within and between sites and initial sampling strata across the Challenger Plateau and Chatham Rise. Data used came from four different fauna collection methods: DTIS video; seamount sled; still images taken along the DTIS video; and beam trawls.
Published
Last updated
ISBN Online
978-0-478-38880-0
ISSN Online
1179-6480
AEBR 098 Review of necropsy records for bycaught NZ sea lions (Phocarctos hookeri), 2000 – 2008
Report - Aquatic Environment and Biodiversity (AEBR)
Subjects
News & Resources, Publications
The development and retrospective application of a system of trauma classification to all sea lions captured from 1999/00 to 2007/08 is discussed, and results compared across years and between groups (e.g. SLED versus non-SLED captures). A lack of brain examinations in the years before 2006/07, in combination with difficulties in interpreting lesions from frozen cadavers, means that this retrospective review has some limitations.
Published
Last updated
ISBN Online
978-0-478-40046-5
ISSN Online
1179-6480
AEBR 099 Rhodolith Beds in Northern New Zealand: Characterisation of Associated Biodiversity and Vulnerability to Environmental Stressors
Report - Aquatic Environment and Biodiversity (AEBR)
Subjects
News & Resources, Publications
Rhodolith beds in New Zealand harboured high diversity of associated macroalgae and invertebrates, undescribed taxa as well new records and range extensions of known species. Subtidal beds were investigated, examining structure and physical characteristics at two locations in the Bay of Islands, and characterising two species, Lithothamnion crispatum and Sporolithon durum. Responses of these rhodolith species to environmental stressors were also investigated both in the field and in culture.
Published
Last updated
ISBN Online
978-0-478-40077-9
ISSN Online
1179-6480
FAR 2021/14 Review and summary of the time series of input data available for the assessment of southern blue whiting (Micromesistius australis) stocks up to and including the 2019 season
This document summarises the observational and research data for southern blue whiting to 2019. Included here are time series of relative abundance from the wide area R.V. Tangaroa acoustic surveys, as well as from local area aggregation industry vessel acoustic surveys, CPUE indices for Bounty Platform and Campbell Island Rise, and trawl survey indices for the Auckland Islands Shelf, Campbell Island Rise, and Pukaki Rise, as well as updated time series of length-at-age and catch-at-age.