• No results found

Management implications of climate change effect on fisheries in Western Australia Part 1: Environmental change and risk assessment

N/A
N/A
Protected

Academic year: 2023

Share "Management implications of climate change effect on fisheries in Western Australia Part 1: Environmental change and risk assessment "

Copied!
182
0
0

Loading.... (view fulltext now)

Full text

Managing the impact of climate change on fisheries in Western Australia Part 1: Environmental change and risk assessment. Management implications of the impact of climate change on fisheries in Western Australia, Part 1: Environmental change and risk assessment.

Non-technical summary

The climate change projection with OFAM produced a decrease in LC with reduced eddy activity. The decline in puerulus populations over the past seven years appears to be due to long-term environmental trends that make the fishery a good candidate to study responses to climate change.

Acknowledgements

Background

There were also short-term (and some longer-term) range expansions of a number of tropical species. The effect on long-lived species cannot be observed for a number of years due to the delay between spawning and recruitment to the fishery.

Need

Objectives

Methods

Climate change effects on marine environment

Historic climate change trends

Marine heatwave

Sea surface temperature interpolation V2 (OIv2). http://www.ncdc.noaa.gov. resolution 1982 pending Global sea surface 1 km. In regions where in situ measurements were not available, satellite SSTs were obtained to assess conditions relevant to specific fisheries in Exmouth Bay, Shark Bay and the Abrolhos Islands over the past 3 years.

Projected climate change trends

The ROMS model uses a terrain-following coordinate system that provides higher resolution than the OFAM model in coastal regions (Table 6.1.2). Annual mean Leeuwin current transport (Sv) and trend (Sv per decade) in the five IPCC models during 1950–1999.

Table 6.1.2.   Configuration and parameters for the OFAM and ROMS models.
Table 6.1.2. Configuration and parameters for the OFAM and ROMS models.

Effect of climate change on fish stocks

Case Studies

Several skill measures have been developed to assess the performance of the IPCC global coupled climate model projections. The historical long-term trends of the environmental variables as well as available projected trends were examined.

Risk assessment

The rank of exposure (or likelihood) used in the risk assessment of species to climate change. The risk assessment of species to climate change obtained by combining sensitivity and exposure.

Table 6.2.1.   The four attributes for each of the three measures of sensitivity, abundance,  distribution and phenology (from Pecl et al
Table 6.2.1. The four attributes for each of the three measures of sensitivity, abundance, distribution and phenology (from Pecl et al

Marine heat wave

The lack of continuous in-situ SST measurements in the region necessitated the use of satellite-derived "blended" or "optimal interpolation (OI)" SSTs that combine multiple satellite sensor, ship, and gauge measurements to create a global data set without gaps. Shark's bay crabs: (i) standardized catch rate of legal size crabs obtained from monthly fishermen's returns by financial year taking into account fishing month and location; and (ii) catch rates of legal-sized crabs in deep water around November of each year;

Development of management policies

Reduced recruitment in the Western Rock Lobster fishery over seven years and the effect of the 2010/11 marine heat wave on abalone, scallop, crab, shrimp and finfish stocks in the Gascoyne and mid-west have provided real-life examples of long-term . term difference in a fishing and an extreme event. The western rock lobster and the effect of the heat wave on invertebrate and small fish fisheries are treated as key case studies that have required research, management and industry to adapt to the major changes taking place in these fisheries.

Results/Discussion

Climate change effects on marine environment

Historic climate change trends

Low-frequency filtered sea levels in the eastern (region A) and western Pacific (region B) and their relation to Fremantle sea level (adapted from Feng et al. 2010). Linear Indian Ocean sea surface temperature trend during Hadley Center SST derived.

Figure 7.1.1.   (Top) Sea surface temperature anomaly pattern during a positive (warm) phase  of the PDO
Figure 7.1.1. (Top) Sea surface temperature anomaly pattern during a positive (warm) phase of the PDO

Marine heat wave – Ningaloo Niño

Monthly SST anomalies (OIv2 dataset) for Exmouth Bay, Shark Bay and the Abrolhos Islands for the locations shown in Figure 7.1.12a. The cooling event during January 2013 corresponds to the intrusion of water into Peshkaqen Bay shown in Figure 7.1.15b.

Figure 7.1.8.   Monthly values of the Southern Oscillation Index (black), the anomaly of Fremantle  sea level (blue) and the anomaly of sea-surface temperature at the Abrolhos  Islands (SST, red) between (a) 1980 and early 2013, and (b) over the last decad
Figure 7.1.8. Monthly values of the Southern Oscillation Index (black), the anomaly of Fremantle sea level (blue) and the anomaly of sea-surface temperature at the Abrolhos Islands (SST, red) between (a) 1980 and early 2013, and (b) over the last decad

Projected climate change trends

From the 1990s to the 2060s, the seasonal mean sea surface temperature (SST) increases for all seasons (Figure 7.1.22). To assess the changes in coastal transport along the coast, the meridional flow is integrated in depth and integrated from the coast to the offshore boundary of the current (Figure 7.1.24). To determine the factors controlling the northward transport in the Cape Current, the coastal meridional transport is plotted against the along-shelf wind stress (Figure 7.1.29a) and the along-shelf sea surface height (SSH) gradient (Figure 7.1.29b).

The vertical velocity is compared with the along-shelf wind stress (Figure 7.1.32a,b) and the local near-bottom meridional velocity (Figure 7.1.32c,d).

Figure 7.1.18.   Annual mean temperature (ºC) of the upper 100 m from the OFAM for the 1990s  (top left) along with the observed values from Locarnini et al
Figure 7.1.18. Annual mean temperature (ºC) of the upper 100 m from the OFAM for the 1990s (top left) along with the observed values from Locarnini et al

Effect of climate change on fish stocks

Case Studies

Therefore, there is uncertainty about the short-term trend of the Leeuwin Current and its potential impact on fisheries. Cyclones had a strongly positive and strongly negative effect on tiger prawn recruitment in Exmouth Bay, depending on the timing of the cyclone and its intensity (Penn and Caputi 1986). Cyclone Vance, which crossed Exmouth Bay in April 1999, had a positive effect on recruitment that year, but also significantly destroyed seagrass nursery habitat, which negatively affected recruitment in the following two years (Loneragan et al. 2013).

Pearl Oysters • Environmental trends in SST, rainfall and north winds and general effect on recruitment.

Table 7.2.1.1:   Summary of environmental effects (positive or negative) on some of the biological  characteristics of species and the long-term trend of the environmental variables  (LC=Leeuwin Current)
Table 7.2.1.1: Summary of environmental effects (positive or negative) on some of the biological characteristics of species and the long-term trend of the environmental variables (LC=Leeuwin Current)

Risk assessments

These trends were then used in the assessment of exposure (probability) of species to climate change occurring based on historical and projected trends and the assessment of overall risk to climate change = sensitivity x exposure (Table 7.2.2.3). After taking exposure into account, the assessment identified Perth Herring, Roe's Abalone, Black Bream, Western Lobster, Pink Snapper, Whiskered Shark, Tiger Prawns, Scallops, Blue Swimmer Crabs and Australian Herring as having the greatest risk from climate change ( Table 7.2 .2.3). This helped determine the climate change priorities for research/management by considering risk associated with climate change as well as the socio-economic importance of the fisheries in the bioregions.

Priority for research and management for climate change issues takes into account the socio-economic importance.

Table 7.2.2.1:   Risk screening of WA’s commercial and recreational finfish and invertebrate species,  based on criteria developed by the South-East Australian Climate Change group  (Pecl et al
Table 7.2.2.1: Risk screening of WA’s commercial and recreational finfish and invertebrate species, based on criteria developed by the South-East Australian Climate Change group (Pecl et al

Western Rock Lobster major case study

The implications of the extended period of low settlement on the stock status and management of the fishery were investigated using a spatial stock assessment model (de Lestang et al. 2012). An important component of the model and management of the fishery was the use of the puerulus settlement to predict the recruitment to the fishery 3-4 years in advance (de Lestang et al. 2009). The size of the migrating crayfish is related to the water temperature around the time of puerulus establishment (about 4 years before).

Annual puerulus settlement of the Western Rock Lobster fishery at various locations throughout the fishery.

Figure 7.2.3.1.  Annual puerulus settlement of the Western Rock Lobster fishery at various locations  throughout the fishery.
Figure 7.2.3.1. Annual puerulus settlement of the Western Rock Lobster fishery at various locations throughout the fishery.

Marine heat wave major case study: invertebrate fisheries

The first was during the previous summer period (December-January) which preceded the winter spawning and the second was during the spawning period (April to June) (Figure 7.2.4.7 top). Correlations between annual scallop recruitment index (log transformed) in northern Shark Bay (top) and Denham Sound (bottom) (November year t) and monthly SST for the previous 2 years. Correlations between Shark Bay's annual recruitment index (log transformed) for king (top) and tiger (bottom) shrimp (March–April year t) and monthly SST in the current and previous year.

Correlations between the Exmouth Gulf annual recruitment index (log transformed) of tiger prawns (March–April year t) and the current and previous year monthly SST.

Figure 7.2.4.1.  Commercial standardised trap crab catch rate (top) and November trawl survey legal  catch rate (bottom)
Figure 7.2.4.1. Commercial standardised trap crab catch rate (top) and November trawl survey legal catch rate (bottom)

Marine heat wave case study: finfish stocks

Monitor the recovery of stocks affected by the heat wave and review the management measures (and possible improvements) needed to promote their recovery. Records available since the "marine heat wave" have revealed a wider distribution in metropolitan waters, with the first records of this species from protected riparian waters of Cockburn Sound, and a presence in metropolitan waters outside the warmer months of the year. This species now contributes to both commercial and recreational catches from the marine waters off metropolitan Perth, more than 600km south of the former southern limit of this species' breeding population.

However, it is currently difficult to determine how representative such online community databases are of the actual relative abundance of the species they record.

Development of management policies

Stock assessment modeling indicated that continued heavy fishing would result in the egg production reference level of the harvest strategy being exceeded within a few years. Many of the main management issues highlighted in the case studies focus on the changes in density and distribution of species, particularly in cases where there are fixed management zones (Table 7.3.1). These pre-recruitment measures also allow for early fishing planning at the level of fishing (and catch) likely to occur in the upcoming season.

This is an example of increasing the resilience of the biological and socio-economic system to climate change for this fishery.

Table 7.3.1.    Summary of key management issues associated with current and projected climate  change effects.
Table 7.3.1. Summary of key management issues associated with current and projected climate change effects.

Benefits and adoption

Further Development

Assessment of this issue would be based on coupled atmosphere-ocean models that examine heat wave events and projected effects under decadal and long-term climate change. Previous research has shown that long-term (30–50 year) increases in water temperature off WA were largely concentrated in the fall/winter period with little or no long-term increases in spring/summer ( Caputi et al. 2009 ). Pre-recruitment information enables early detection of changes in abundance that allow appropriate assessment and management recommendations before fishing in lean year classes.

The possible effect on the recruitment and adult stocks of fisheries will need to be assessed as data become available on the age structure of key indicator species such as Snapper.

Planned outcomes

Discussion and Conclusions

The effect of environment on the puerulus settlement of the Western Rock Lobster (Panulirus cygnus) in Western Australia. Evaluation of source-sink relationships for the western rock lobster fishery using oceanographic modeling (FRDC project 2008/087). Dynamics and impact of the Leeuwin Current on the marine environment off Western Australia, Perth, Western Australia.

Spatial and temporal differences in size at maturity of the lobster Panulirus cygnus George.

Intellectual Property

Staff List

Please list the various unit stocks for this species and any relevant climate change issues. Please list the different unit stocks for this species and any relevant climate change issues A. Please list the different unit stocks for this species and any relevant climate change issues Total risk ranking 5.5.

List the various unit stocks for this species and any significant climate change issues Overall Risk Classification 5.5 A.

Figure

Table 6.1.1.   Environmental data from internet sources and measurements by Department of  Fisheries (DoF) staff and other agencies.
Table 6.1.2.   Configuration and parameters for the OFAM and ROMS models.
Figure 6.1.1.   The upper 200 m depth-averaged velocity field, where the current speed (m/s) is  represented by the colour scale on the right and the arrows indicate direction
Figure 6.1.2.   (a) Full ROMS model domain. The 100 m isobath is indicated by the pink line and  the coastline by the black line, water depths less than 30 m being masked as land
+7

References

Related documents

Centre Number Student Number 2014 HIGHER SCHOOL CERTIFICATE EXAMINATION Indonesian Continuers General Instructions • Reading time – 10 minutes • Working time – 2 hours and 50