Metanephrops Challengeri) in the Bay of Plenty (SCI 1

Metanephrops Challengeri) in the Bay of Plenty (SCI 1

New Zealand Aquatic Environment and Biodiversity Report No. 42 2009 ISSN 1176-9440 Ecosystem indicators for New Zealand fisheries Ian Tuck Russell Cole Jennifer Devine Ecosystem indicators for New Zealand fisheries Ian Tuck1 Russell Cole2 Jennifer Devine3 1NIWA Private Bag 99940 Auckland 1149 2NIWA P O Box 893 Nelson 7040 3NIWA Private Bag 14901 Wellington 6241 New Zealand Aquatic Environment and Biodiversity Report No. 42 2009 Published by Ministry of Fisheries Wellington 2009 ISSN 1176-9440 © Ministry of Fisheries 2009 Tuck, I.; Cole, R.; Devine, J. (2009). Ecosystem indicators for New Zealand fisheries. New Zealand Aquatic Environment and Biodiversity Report No. 42. 188 p. This series continues the Marine Biodiversity Biosecurity Report series which ceased with No. 7 in February 2005. CONTENTS EXECUTIVE SUMMARY...........................................................................................................................5 1. INTRODUCTION.................................................................................................................................6 2. FISH-BASED ECOSYSTEM INDICATORS......................................................................................7 2.1. Species based indicators (SpBIs) .................................................................................................7 2.1.1. Indicator or endangered species...............................................................................................8 2.1.2. Diversity ..................................................................................................................................8 2.1.3. Dominance and Abundance Biomass Comparison (ABC) curves .........................................9 2.1.4. Absolute and relative species abundance ................................................................................9 2.1.5. Exploitation rate ......................................................................................................................9 2.1.6. Genetic diversity....................................................................................................................10 2.1.7. Species distribution................................................................................................................10 2.1.8. Proportion of non-commercial species ..................................................................................10 2.2. Size-based indicators (SBIs) ......................................................................................................10 2.2.1. Mean or maximum fish length (or weight) of population / community ................................10 2.2.2. Mean length at age in a population........................................................................................11 2.2.3. Fulton’s condition index........................................................................................................12 2.2.4. Proportion of large (individuals) species in (population) community...................................12 2.2.5. Mean length (or age) at maturity of population / community................................................12 2.2.6. Slope and intercept of biomass or abundance size (weight or length) spectra ......................12 2.2.7. Slope and intercept of diversity size spectra..........................................................................13 2.2.8. Size distribution of species....................................................................................................13 2.3. Trophodynamic indicators (TIs) ................................................................................................13 2.3.1. Catch or biomass ratios..........................................................................................................14 2.3.2. Trophic Level (TL) of the catch ............................................................................................14 2.3.3. Trophic spectra ......................................................................................................................14 2.4. Indicators considered .................................................................................................................15 3. New Zealand Trawl surveys................................................................................................................15 3.1. Inshore surveys ..........................................................................................................................18 3.1.1. Bay of Plenty surveys............................................................................................................18 3.1.2. West coast North Island surveys............................................................................................18 3.1.3. Hauraki Gulf surveys.............................................................................................................19 3.1.4. East coast South island ..........................................................................................................19 3.1.5. West coast South island.........................................................................................................19 3.2. Middle depth trawl surveys........................................................................................................19 3.2.1. Scampi trawl surveys.............................................................................................................20 3.2.2. Chatham Rise hoki trawl surveys ..........................................................................................20 3.2.3. Southland and Sub-Antarctic trawl survey............................................................................20 3.3. Deepwater surveys.....................................................................................................................20 3.3.1. Orange roughy on the Chatham Rise.....................................................................................21 3.3.2. Orange roughy on the Challenger Plateau.............................................................................21 3.4. Survey series for examination of indicators...............................................................................21 3.5. Effort data ..................................................................................................................................21 4. HAURAKI GULF SURVEYS............................................................................................................22 4.1. Analysis of catch weight by station ...........................................................................................24 4.1.1. Species based indicators ........................................................................................................24 4.1.1.1. Indicator / endangered species ......................................................................................24 4.1.1.2. Species distribution index.............................................................................................28 4.1.1.3. Diversity indicators.......................................................................................................29 4.1.1.4. Comparison across data sets .........................................................................................30 4.1.2. Trophodynamic indicators.....................................................................................................41 4.1.2.1. Biomass ratio ................................................................................................................41 4.1.2.2. Trophic Level of the catch ............................................................................................41 4.1.2.3. Trophic spectra .............................................................................................................41 3 4.2. Analysis of catch numbers at length by station..........................................................................48 4.2.1. Median and L95 size..............................................................................................................48 4.2.2. Proportion of large individuals..............................................................................................49 4.2.3. W statistic ..............................................................................................................................49 4.2.4. Abundance and biomass size spectra.....................................................................................55 4.2.5. Diversity spectra....................................................................................................................62 4.3. Effort patterns ............................................................................................................................67 4.4. Comparison across indicators and relationship with fishing effort............................................69 5. CHATHAM RISE MIDDLE DEPTHS SURVEYS ...........................................................................70 5.1. Analysis of catch weight by station ...........................................................................................72 5.1.1. Species-based indicators........................................................................................................72 5.1.1.1. Indicator / endangered species ......................................................................................72 5.1.1.2. Species distribution index.............................................................................................73

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