Research and data notes
This page contains information about how deepwater fisheries data are collected and reported.
Collecting and reporting deepwater fisheries data
Ministry for Primary Industries (MPI) Observers collect data on catch, bycatch and discards, on about 25% of commercial deepwater trawls.
NIWA scientists analyse these data and use them to estimate the bycatch and discards in relation to the total reported catch. This is a technical procedure that requires the observer data to be stratified (e.g. by area, month) and scaled up to the total reported (or landed) target species catch, providing estimates of mean catch with error bounds. These error bounds are not shown here.
NIWA is contracted by MPI to carry out updates to these reports to provide ongoing monitoring of catch, bycatch and discard ratios levels. Each year we update the report for one of the key fisheries. This is necessary as fishing technology and practices and the relative abundance of species are constantly changing.
The earliest data used in the analyses go back to 1991. In early analyses commercial species bycatch was grouped as “commercial”, not QMS. For this summary we have assumed these to be the same.
Proportion of deepwater trawls with observers
Using a weighted average across the last five years available data for the six fisheries described in this section, we estimate there was observer coverage on about 25% of deepwater trawls.
Observer coverage from the last 11 years was about 19%, indicating an increase in observer coverage on board deep sea trawlers in recent years.
Data references
The following is a list of references of reports that we have used to compile this data.
Anderson, O. F. (2008) Fish and invertebrate bycatch and discards in ling longline fisheries, 1998-2006. New Zealand Aquatic Environment and Biodiversity Report 23. 43 p.
Anderson, O. F. (2009) Fish and invertebrate bycatch and discards in southern blue whiting fisheries, 2002-07. New Zealand Aquatic Environment and Biodiversity Report 43. 42 p.
Anderson, O. F. (2011) Fish and invertebrate bycatch and discards in orange roughy and oreo fisheries from 1990-91 until 2008-09. New Zealand Aquatic Environment and Biodiversity Report 67. 60 p.
Anderson, O. F. (2012) Fish and invertebrate bycatch and discards in New Zealand scampi fisheries from 1990-91 until 2009-10. New Zealand Aquatic Environment and Biodiversity Report 100. 65 p.
Anderson, O. F. (2013) Fish and invertebrate bycatch and discards in New Zealand arrow squid fisheries from 1990-91 until 2010-11. New Zealand Aquatic Environment and Biodiversity Report 112. 62 p.
Anderson, O. F. (2014) Fish and invertebrate bycatch and discards in ling longline fisheries from 1992-93 until 2011-12. New Zealand Aquatic Environment and Biodiversity Report 138. 66 p.
Ballara, S. L.; O’Driscoll, R. L. (2015). Fish and invertebrate bycatch and discards in New Zealand hoki, hake or ling trawl fisheries from 1990-91 until 2012-13. New Zealand Aquatic Environment and Biodiversity Report 163. 120 p.
