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This report provides a comprehensive description of the Exmouth Gulf Prawn Managed Fishery (EGPMF) in Western Australia and contains information relevant to assisting the assessment of this fishery against the Marine Stewardship Council (MSC) standard (v1.3) for sustainable fishing. Retained species as a percentage of the total annual retained catch for the Exmouth Gulf Prawn Managed Fishery.

Figure 1.1.  Locality of Exmouth Gulf  (black box)  within the Gascoyne Coast Bioregion of  Western Australia
Figure 1.1. Locality of Exmouth Gulf (black box) within the Gascoyne Coast Bioregion of Western Australia

Brown Tiger Prawn

Taxonomy and Distribution

Key habitats in the Gulf include mangroves, intertidal mudflats, coral reef, seagrass and mud/sand bottom areas. The Gulf is home to many species of tropical fish and invertebrates, as well as protected species such as dolphins, sea turtles, sticklebacks (e.g. sawfish), sea snakes and seahorses, and tubes.

Stock Structure

Life History

As pre-adults, brown tiger shrimp migrate out of the rearing areas to deeper water to spawn. Several values ​​of natural mortality (M) of brown tiger shrimp have been described in the published literature.

Figure  2.3. Life cycle of a penaeid prawn (modified from NSW Department of Industry and  Investment 2010)
Figure 2.3. Life cycle of a penaeid prawn (modified from NSW Department of Industry and Investment 2010)

Western King Prawn

Taxonomy and Distribution

This latter value was used by Hall and Watson (1999) for brown tiger prawns in Shark Bay. The western king shrimp is widely distributed throughout the Indo-West Pacific region (Gray et al. 1983).

Stock Structure

There are two major western king prawn fisheries in WA in Shark Bay and Exmouth Gulf, with smaller quantities landed in the North Coast bioregion from prawn fisheries operating at Onslow and Broome.

Life History

The fecundity of western king prawns in WA is positively related to the size of the prawn (Penn 1980). Faster development and higher survival rates of western king prawns have been observed with increasing water temperatures (Rodgers et al. 2013).

Development of Fishery

A collapse of the brown tiger shrimp stock in Exmouth Gulf in the early 1980s (see below in Section 3.3) led to increased monitoring and the implementation of additional fishery closures (Kangas et al. 2008). The boundaries of the EGPMF and the size of the permanently closed areas as legally defined in the management plan are outlined in Figure 3.1.

Fishing Gear and Methods

This ensures that shrimp disturbed by the floor chain do not cross the headline and thus maintain the catch efficiency of the nets. Trawling by vessels in the EGPMF generally occurs in about 30% of the Gulf of Exmouth each season, and the Gulf was trawled with trawl nets.

Figure  3.2.  Standard  historical  twin-rig otter trawl (a) and current  quad-rig otter trawl (b)  configurations used in the EGPMF (Adapted from Stirling 1998)
Figure 3.2. Standard historical twin-rig otter trawl (a) and current quad-rig otter trawl (b) configurations used in the EGPMF (Adapted from Stirling 1998)

Overview of Catch and Effort

Analysis of the spatial distribution of catches from logbook data (see section 8.4.2.1.1 for more details) shows that the majority of brown tiger shrimp catches are taken in the central areas off the Gulf, while western king prawns are mainly fished in the Northern area (Figure 3.1). Below is an overview of the fisheries specific governance and management related to the EGPMF.

Figure 3.3). Landings of both target species in Exmouth Gulf then remained relatively stable  until 2000, when a substantial decline in stock levels (particularly of brown tiger prawns)  associated with impacts of the Category 5 Cyclone Vance  was observed
Figure 3.3). Landings of both target species in Exmouth Gulf then remained relatively stable until 2000, when a substantial decline in stock levels (particularly of brown tiger prawns) associated with impacts of the Category 5 Cyclone Vance was observed

Management System

  • FRMA
  • FRMR
  • Management Plan
  • Determinations by the Director General (Chief Executive Officer)
  • Exemptions
  • Managed Fishery Licence Conditions
  • Section 43 Orders

There is also the power to determine the fishing capacity on the basis of a management plan (Article 59). The EGPMF is closed to fishing between November and March/April each year under Article 10 of the Management Plan (see section 4.1.4 below).

Harvest Strategy

Bycatch Action Plan

Cooperative Management Framework

Customary and Recreational Fishing

Marine Protected Areas

State Marine Protected Areas

Commonwealth Marine Parks and Reserves

Ningaloo Marine Park and Muiron Islands Marine Management Area and areas of overlap with the northwestern waters of the EGPMF. The North-west Commonwealth Marine Reserves Network6 covers 335,437 km2 and includes 13 Commonwealth Marine Reserves in waters outside state waters (beyond three nautical miles).

ESD Reporting and Risk Assessments

As an update to this initial risk assessment for the fishery, an internal risk assessment for EGPMF was completed in 2008. Additionally, in 2014, an internal risk assessment was conducted on the target, by-product, bycatch and ETP species for EGPMF using Productivity Sensitivity Analysis Methodology (PSA).

Assessments and Certifications

As there have been a number of significant changes in the fishery since 2001, the aim of the internal risk assessment workshop was to review the risk classifications identified in 2001 and determine whether they were still relevant or whether they needed to be changed. The main external influences outlined here for the EGPMF are (1) catches of the target stocks by other fisheries, (2) market influences, (3) environmental factors and (4) other activities, such as oil and gas exploration.

Catch from Other Fisheries

External influences include other activities and factors occurring in the Exmouth Bay region that may or may not affect the productivity and sustainability of fisheries resources and their ecosystems.

Market Influences

Environmental Factors

When the seagrass recovered after 2 – 3 years, brown tiger shrimp landings increased to their precyclone levels (Loneragan et al. 2004). The 2010/11 marine heat wave event in WA (Pearce et al. 2011), and continued higher than average temperatures in the summers of 2012 and 2013, may have contributed to recent extremes in brown tiger shrimp abundance in Exmouth Gulf.

Other Activities

This project is considered a high priority for the department and funding has recently been secured. While these abundance indices are important indicators for the stocks, other information collected during the season (e.g. commercial catches, effort and environmental data, see section 8.4 Monitoring) is also evaluated to provide insight into e.g. environmental factors influencing shrimp recruitment .

Current Stock Status

Brown Tiger Prawns

Due to reduced fishing effort during these years, brown tiger shrimp landings were as low as recorded in the history of the fishery (46 t in 2012 and 95 t in 2013)10. In 2014, the start of the season was again delayed, despite the brown tiger shrimp recovery index being just above the target for the start of the fishery, to prevent an early harvest of western king prawns (see below).

Figure 6.1.  Mean spawning stock index (kg / hr) for brown tiger prawns in Exmouth Gulf  between 1970 and 2014, relative to the target and limit reference points (25 and  10 kg / hr, respectively)
Figure 6.1. Mean spawning stock index (kg / hr) for brown tiger prawns in Exmouth Gulf between 1970 and 2014, relative to the target and limit reference points (25 and 10 kg / hr, respectively)

Western King Prawns

As a result of the low recruitment index in 2014, fishing on the western king prawn grounds was delayed until mid-July (with additional surveys conducted in May and June), reducing overall effort on this species. Average spawning stock index for western king prawns (commercial catch rates (kg/hr) in areas R1 and S2 in August and September) in Exmouth Gulf between 1998 and 2014, relative to target (25 kg/hr) and limit (15 kg)/hr) reference points.

Figure 6.3.  Mean western king prawn spawning stock index (commercial catch rates (kg / hr)  of  in areas R1 and S2  during  August  and September)  in Exmouth Gulf between  1998  and  2014, relative to the target  (25 kg / hr)  and limit (15 kg / hr)  ref
Figure 6.3. Mean western king prawn spawning stock index (commercial catch rates (kg / hr) of in areas R1 and S2 during August and September) in Exmouth Gulf between 1998 and 2014, relative to the target (25 kg / hr) and limit (15 kg / hr) ref

Assessment Description

Recruitment Indices

Spawning Stock Indices

Commercial Catch Rate Monitoring

Appropriateness of Assessment

Assessment Approach

Uncertainty in the Assessment

Uncertainty in the spawning stock index for western king prawns, which is based on fishery-dependent catch rates, is handled by considering only catch and effort in those fishing grounds that are clearly identified as dominated by western king prawns and represent key spawning grounds for this species. Each carton is accurately weighed on board the boat and when unloaded, each carton (of the different species and shrimp size grades) is counted by the trucking company and the total weight per grade is provided to the Department.

Evaluation of Assessment

Uncertainty in total landings is accounted for by checking commercial catch data against processor landings. Uncertainty in the behavior of the fishing fleet is reduced by regular communication with fishermen covering the entire fleet (sometimes daily).

Peer Review of Assessment

Framework

  • Design
  • Evaluation
  • Monitoring
  • Review

Catch rate of brown tiger prawns in the Central TPSA during October spawning stock survey. By the following year, the spawning stock was back at the target level, demonstrating the effectiveness of the harvest strategy.

Table 8.1.   Summary of current performance indicators, reference points, control rules and justification for brown tiger and western king prawns  in the Exmouth Gulf Prawn Managed Fishery
Table 8.1. Summary of current performance indicators, reference points, control rules and justification for brown tiger and western king prawns in the Exmouth Gulf Prawn Managed Fishery
  • Appropriateness of Reference Points
  • Level of Target Reference Points
  • Level of Threshold Reference Points
  • Level of Limit Reference Points

The target spawning stock catch rate of 25 kg/hour for brown tiger shrimp is well above the breakpoint on the current SRR curve (Figure 8.1). The catch rate limit of 10 kg/h for brown tiger shrimp applies to both the recruitment index (below which fishing for this species does not commence) and the spawning stock index (Table 8.1).

Figure  8.1. Relationship between spring spawning stock, autumn recruitment and January- January-February rainfall for the Exmouth Gulf brown tiger prawn stock, including three  regression lines representing the expected recruitment under January and  Febr
Figure 8.1. Relationship between spring spawning stock, autumn recruitment and January- January-February rainfall for the Exmouth Gulf brown tiger prawn stock, including three regression lines representing the expected recruitment under January and Febr

Control Rules and Tools

Design and Application

Central TPSA and Eastern Area closed to fishing when the commercial catch rate falls below the target level, or at the start of the lunar closure in August (whichever comes first). If the brown tiger prawn spawning stock index is well above the target level (25 kg/hr) after the second spawning stock survey, then the timing and reopening of the central TPSA and the eastern area will be considered in consultation with the industry.

Figure 8.4. Flowchart of the general annual harvest strategy operations in the EGPMF
Figure 8.4. Flowchart of the general annual harvest strategy operations in the EGPMF

Accounting for Uncertainty

Catch rates above target levels result in no change in season management adjustments for the following year. Catch rates below the target level (at the threshold limit) trigger a review of management arrangements for the following season, which may then result in management action if sustainability is deemed to be at risk.

Evaluation

Information and Monitoring

Range of Information

In addition to a wealth of biological information available from studies of brown tiger and western king prawns in Exmouth Gulf (see Section 2.1), several other research projects focusing on this fishery have been undertaken over the past two decades. As part of an FRDC-funded study on brown tiger prawn stock enhancement, the distribution of seagrass and algal communities in both the eastern and western parts of Exmouth Gulf was sampled between 1999 and 2001 (Kenyon et al. 2003).

Table 8.3. Summary of monitoring activities in the EGPMF  Data type
Table 8.3. Summary of monitoring activities in the EGPMF Data type

Monitoring

In 2006, the annual landings of brown tiger prawns were moderate (258 t) and landings of western king prawns relatively high (442 t). In 2011, the annual landings of brown tiger prawns were very high (749 t) and western king prawn landings very low (97 t).

Figure 8.5. Fishing grounds in Exmouth Gulf used for analysis of catch and effort data Nursery area
Figure 8.5. Fishing grounds in Exmouth Gulf used for analysis of catch and effort data Nursery area

Comprehensiveness of Information

At each survey site, the representative sample of brown tiger prawns collected from the trawl is slaughtered (to provide sex ratio information), measured and the prevalence of parasites noted. Sex-ratio information during the spawning period can be important to supplement catch rate information when assessing the performance of the fishery.

BRD Trials and Bycatch Composition

More recent information on bycatch in the EPGMF is available from square mesh fishery trials in 2008 and 2009. The permit holder in the EPGMF has now modified the square mesh panel to avoid reduction in size and in a central position.

Figure  9.1. Diagrammatic representation of (a) the super shooter grid used in Exmouth Gulf  and (b) its location in the prawn trawl net (Source: Kangas & Thomson 2004)
Figure 9.1. Diagrammatic representation of (a) the super shooter grid used in Exmouth Gulf and (b) its location in the prawn trawl net (Source: Kangas & Thomson 2004)

Bioregional Risk Assessment

Elasmobranchs scored highly in the risk assessment, earning nine of the top 20 rankings in the Gascoyne Coast Bioregion. Turtles in the Gascoyne Coast Bioregion had a moderate risk category, while all other species (i.e., sea snakes, cormorants and syngnathids) had a low or low-moderate risk (Evans & Molony 2010).

Ecosystem Impacts of Trawling

There were significant differences in richness, evenness and diversity indices among the four groups. Invertebrate species experienced significant seasonal declines in abundance between the beginning, middle, and end of the 2004 season for both trawled and nontrawled sites (Kangas et al. 2007).

Figure 9.3. Sampling sites in Exmouth Gulf and Onslow Area 1 used by Kangas et al. (2007)
Figure 9.3. Sampling sites in Exmouth Gulf and Onslow Area 1 used by Kangas et al. (2007)

Fishery Impacts

Main Retained Species

In 2014, the provisional blue shrimp catch (to the end of October) was 94 t, and effort was again low for the year (Fletcher and Santoro 2014). In addition, the breeding biomass of blue shrimp in the EGPMF is likely to be at sustainable levels because a significant portion of the biomass is protected by the spawning closures of the brown tiger shrimp.

Risk Assessment Outcomes

Blue shrimp are considered to be more resistant to fishing pressure due to their smaller size and lower catchability, as well as the lower level of fishing in the Gulf of Exmouth compared to brown tiger shrimp and western king shrimp (Kangas et al. 2006). The distribution of blue shrimp in the Gulf of Exmouth overlaps that of brown tiger shrimp, and fishing takes place at different levels depending on the abundance of (and thus the fishing effort exerted on) the more valuable brown tiger shrimp.

Retained Species Management

Catches of the main conserved non-target species have remained stable over the history of the fishery, with any decline in catches generally due to effort reductions or environmental factors affecting species richness on trawl grounds (e.g. banana shrimp). In addition, additional measures have been taken to reduce the impact of fishing on blue swimmer crab populations, including a voluntary minimum commercial size (137 mm spine to spine) for blue swimmer crabs, which is larger than the legal minimum size (127 mm spine to spine). ), and a ban on holding egg-bearing females.

Retained Species Information and Monitoring

If monitoring indicates a need to reduce the impacts of fisheries on by-product species in Exmouth Bay, this could be achieved through expanding the use of current management tools, such as spatial and temporal closures, targeted harvest strategies to optimize effort expenditure , a reduction in overall fishing. effort and use of mechanical or other equipment, such as BRD and hoppers / handling techniques. Overall evidence that the strategy is achieving its objective is provided by (1) consistent catch histories of key non-target conservation species and (2) an experimental survey-based study that found no differences in abundance, species richness , the evenness or diversity of fish and invertebrates (including each of the main species held) between fished and undisturbed areas in Exmouth Bay (Kangas et al. 2007).

Fishery impacts

Risk Assessment Outcomes

Small fish species account for the majority of bycatch in the EGPMF (Kangas et al. 2006), and the risk to these species was considered together in the 2008 risk assessment. In addition, it is known from research results that these species also occur in large non-trawled areas of the Gulf (Kangas et al. 2007).

Bycatch Management

Summary of key management changes in the EGPMF that have reduced the impact of the fishery on bycatch species populations (Source: DoF 2014b). There is a continuous monitoring and improvement process to minimize the impact of the trawling gear in the EGPMF.

Figure 11.1. Summary of key management changes in the EGPMF that have reduced the impact  of the fishery on bycatch species populations (Source: DoF 2014b)
Figure 11.1. Summary of key management changes in the EGPMF that have reduced the impact of the fishery on bycatch species populations (Source: DoF 2014b)

Bycatch Information and Monitoring

Sea snakes can be found throughout the Gulf, but are most common in the shallow waters of the eastern coast (Storr et al. 2002; Morrison et al. 2003). Within Exmouth Gulf, they occur primarily along salt marshes and detached algal communities (Kangas et al. 2006).

Fishery Impacts

Risk Assessment Outcomes

In 2013, fishermen in the EGPMF reported interactions with ten turtles, all of which were returned to the water alive. Despite their great abundance in the Gulf, very few green turtles have been reported throughout the history of the fishery (Kangas et al. 2006).

ETP Species Management

In addition, the rates of ETP species interactions reported in fisheries since the implementation of the BRD continue to be very low (see Table 12.1). As such, appropriate performance indicators, reference levels and control rules for ETP types have been developed in the EGPMF (DoF 2014a).

ETP Species Information and Monitoring

These measures have been tested in fisheries and other similar tropical trawl fisheries in Australia and are considered effective based on trial results (see Section 9.1) which have shown a reduction in bycatch of ETP species. Additional information on ETP species was collected through non-fishery surveys conducted by Departmental research staff.

Overview

The mangrove stands are the most extensive along the eastern shores of the Gulf (Johnstone 1990). The majority of the Gulf's flora and fauna is tropical, but some subtropical and temperate species are also present (Hutchins 1994).

Habitat Mapping

The warm waters of the Leeuwin Current affect the inshore waters of Exmouth Bay, particularly during strong winter currents. Further information on the habitats and ecosystem of Exmouth Bay in relation to shrimp fishing activities is available as part of the FRDC funded project, Kangas et al.

Table 13.1.  Biogeomorphological units identified by Lyne et al. (2006) within Exmouth Gulf  Geographic Unit  Description
Table 13.1. Biogeomorphological units identified by Lyne et al. (2006) within Exmouth Gulf Geographic Unit Description

Habitat Assessment

Fishery Impacts

Studies of the actual impacts of shrimp trawling show only minimal impacts on animal communities (e.g. Kangas et al. 2007). Therefore, it is highly likely that EGPMF trawling activities would pose a negligible risk to macroalgal and seagrass habitats (Kangas et al. 2006).

Habitat Management

The habitat performance indicators relate to the extent of the trawled area within the entire fishing area. The fishery distribution in the Gulf has consistently met this requirement, with only 28% of the Gulf being trawled in 2013 (Sporer et al. 2014).

Habitat Information and Monitoring

Sensitive habitats, such as macroalgae and sea grass, are protected in permanently closed nursery areas along the southern and eastern sections of the Gulf. Exmouth Bay includes a number of sensitive habitats which are permanently closed to anglers as part of the nursery area.

Ecosystem Assessment

Fishery Impacts

In trawling on the Great Barrier Reef, a study showed that the majority of discards were fish and that about 40% of the fish floated on return to the water. Shrimp fishing activities in the Gulf of Exmouth are considered 'negligible' in terms of creating a more turbid environment that has the potential to increase the nutrient load of the ecosystem and silt up habitats (Kangas et al. 2006).

Ecosystem Management

Ecosystem Information and Monitoring

The governance and policy section summarizes the broad, high-level context of the fisheries management system within which the EGPMF operates. Consultation processes and policies, as well as the roles and responsibilities of people and organizations within the overarching fisheries management system;

Legal and / or Customary Framework

Compatibility of Laws or Standards with Effective Management

The OCS 1995 stipulates that the State will manage all trawling on the landward side of the 200m isobath in WA, and the Commonwealth will manage all deepwater trawling. Expands the basis of the Act to include aquatic ecosystem issues in the management regulations.

Resolution of Legal Disputes

Importantly, the proposed ARMA includes objectives to: “(a) ensure the environmental sustainability of the state's aquatic resources and aquatic ecosystems for the benefit of present and future generations; and (b) ensure that the aquatic resources of the State are managed, developed and used with due regard to the economic, social and other benefits that the aquatic resources may provide”. All subsidiary legislation is also reviewed by the Joint Standing Committee on Delegated Legislation, which may seek further advice on the reasons for the legislation and may decide not to authorize the legislation.

Respect for Rights

FRMA defines common fishing as:. fishing by an aboriginal person who —. a) is in accordance with the customary aboriginal law and tradition of the area being fished; and. The Department issued a policy position statement in 2009 on customary fisheries in WA (DoF 2009), which states that customary fisheries apply, within a sustainable fisheries management framework, to Aboriginal people who fish in accordance with traditional law and custom. of the area fished and fished for the purpose of meeting personal, domestic, ceremonial, educational or non-commercial communal needs.

Consultation, Roles and Responsibilities

  • Department of Fisheries
  • Peak Sector Bodies
  • Consultation Processes
  • Participation

Providing feedback to the Department on proposed outcomes and budget priorities for Fisheries Research and Development Account expenditures; The establishment of a Water Advisory Committee (AAC) to provide independent advice to the Minister or Department on high-level strategic matters.

Table 14.1. WAFIC
Table 14.1. WAFIC's Commercial Fisheries Consultation Operational Principles

Long-Term Objectives

  • WA Fisheries Legislation
  • Resourcing the Ability to Meet Long-Term Objectives
  • Key Policies for Meeting Long-Term Objectives
  • Aquatic Biodiversity Policy

The government's desired result for the department is conservation and sustainable development of the state's fishing resources. The key principles of ESD are implicit in the objectives of FRMA and the department's ESD policy (Fletcher 2002).

Figure 14.2. General process for completing an ESD report for a fishery
Figure 14.2. General process for completing an ESD report for a fishery

Incentives for Sustainable Fishing

Review Process

Fishery-Specific Objectives

Target Species Stock (P1) Objectives

There is strong evidence to suggest that this management objective is being met in the long term (see section 6). As part of the EGPMF harvest strategy, a review of management arrangements is initiated if the annual performance measure (egg stock index) is below the target level.

Ecosystem (P2) Objectives

This ensures that potential issues are identified and addressed before the next fishing season and that the long-term management objective relevant to MSC Principle 1 continues to be met.

Economic Objective

Although not directly used as a measure of performance against the economic management objective, there are ways in which the economic efficiency of fisheries can be measured. The long-term trend from these data indicates that the management framework allows the fishery to operate efficiently and viable within a sustainable fisheries framework.

Decision-Making Processes

  • Established Processes
  • Responsiveness of Decision-making Processes
  • Use of Precautionary Approach
  • Accountability and Transparency
  • Approach to Disputes

The department must provide documentation for consultation and the results of the decision-making process during this process. This reporting consists of presentations and the delivery of the annual accounts for the fishery.

Figure 15.1 shows the consultation and decision-making process as it relates to the EGPMF  management system
Figure 15.1 shows the consultation and decision-making process as it relates to the EGPMF management system

Compliance and Enforcement

Monitoring, Control and Surveillance Systems

The Department conducts compliance risk assessments every 1 - 2 years in major fisheries (eg EGPMF) or those perceived to be at high risk and every 3 - 5 years in smaller fisheries. There are two levels to the risk assessment process - the first level is the formal transparent process involving industry and other stakeholders, and the second level is internal, using scientists, fisheries managers and compliance staff.

Applying Sanctions

Level of Compliance

Research Plan

Research Plan

Research Results

Monitoring and Management Performance Evaluation

Evaluation Coverage

Internal and External Review

General References (Sections 1 – 5)

MSC Principle 1 References (Sections 6 – 8)

MSC Principle 2 References (Sections 9 – 13)

MSC Principle 3 References (Sections 14 – 15)

Figure

Figure 1.1.  Locality of Exmouth Gulf  (black box)  within the Gascoyne Coast Bioregion of  Western Australia
Figure  2.3. Life cycle of a penaeid prawn (modified from NSW Department of Industry and  Investment 2010)
Figure 3.1. Main fishery boundaries and management areas of the EGPMF
Figure 6.4.  Mean  recruitment index  (kg / hr, ± 95% CI)  for  western king  prawns  in Exmouth  Gulf between 2003 and 2014, relative to the target (30 kg / hr, solid black line) and  limit (15 kg / hr, dashed red line) reference points
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References

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