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Fisheries Occasional Publication No. 138

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The Chief Executive of the Department of Primary Industries and Regional Development and the State of Western Australia accept no liability, whether negligent or otherwise, arising out of the use or release of this information or any part of it.

Executive Summary

Background

Of the 21 workshop options, six were potential gear modifications, which were assessed for their cost and practical use through a series of gear trials with fishermen in late 2013 (How et al. 2015). Results from the workshop and the gear trials resulted in a number of gear modifications being legislated in June 2014, which aimed to reduce whale entanglements (Table 1). An assessment of the management measures was reviewed annually by the Operational Whale Entanglement Reference Group (OWERG); whose membership consisted of fishermen from the spiny lobster and squid fisheries as well as representatives from.

An overview of the gear changes that have been in place since 2016 is set out in Table 1 and illustrated in Figure 1 (full management plan clauses can be found in Appendix 1 – Current Management Arrangements). Shallow water was defined by the depth that could be fished with the maximum unweighted rope component (see Table 2) (adapted from Bellchambers et al. 2017). 138 5 Table 2 Changes in the maximum unweighted rope and season times by season since the gear modifications were introduced.

An evaluation of the effectiveness of gear changes in reducing whale entanglements was conducted (How et al. in preparation). Preliminary results indicate that there has been an approximately 60% reduction in entanglements in lobster fishing gear as a direct result of implementing the gear changes.

Table 1 Summary of gear modification requirements for maximum rope length, surface rope,  floats and float rig length and periods between pulling pots for both shallow and deep  water
Table 1 Summary of gear modification requirements for maximum rope length, surface rope, floats and float rig length and periods between pulling pots for both shallow and deep water

Review Process

Provision of Information

A presentation on whale disentanglement operations was provided by John Edwards (Department of Biodiversity Conservation and Attractions (DBCA); Appendix 5). Compliance around the whale mitigation measures was presented by Mr Todd A'Vard (Department - Appendix 6). The number of fisheries violations committed against each of the management plan clauses was provided with the main issues being: i) too many floats and ii) insufficient or inappropriately positioned weights. The final session for the day consisted of presentations provided by Dr How and Mr Graeme Baudains (Department – ​​Appendix 7).

Dr. How briefed participants on the latest research information specific to the workshop sessions scheduled for the following day. Information was also provided regarding where (i.e., what water depths) in the rock lobster fishery whales migrate, and possibly interact with rock lobster pots. The water depths in which whales migrate depend on the strength of the Leeuwin Current, as whales migrate within the Leeuwin Current.

Reducing the number of pots (or vertical lines) in the water should help reduce the number of entanglements. Workshop participants were given an interactive web page where they could change the maximum number (cap) or use (currently 50%) of pots that could be used in any given month. Changes can then be examined regarding the actual number of pods likely to be caught, how this may affect whale entanglement rates and also the viability of smaller operators.

Sir. Baudains then highlighted the social consequences of whale entanglements, which include risks surrounding public reaction to entanglements and the potential for injury or death to an individual involved in entanglements. Sir. Baudains recommended that industry take the lead in setting a threshold/target level (ie number of entanglements/year) that would trigger further action. The best defense for this social issue is to show the government and the general community that the industry is working to keep reducing the number of entanglements.

Workshop Discussions

  • Gear Changes
  • Definition of, and reduction in, pot usage rates
  • Entanglement Mitigation Season
  • Improved Disentanglements
  • Spatial Closures
  • Other
  • Research

Comment: Modeling and data from satellite-tagged whales indicated that the number of interactions in shallow water (< 20 m) was small compared to deeper depths. Current arrangements: Section 68 (1) of the Plan; The maximum number of pots allowed to be operated under license is the current eligibility times 0.05 (note a slight difference for zone B). An exemption instrument allows twice this number of pots to be used from November to April.

Comment: It was recognized that additional reductions in pot use may be necessary during the whale migration to reduce entanglements. Participants in the industry workshop were of the opinion that the minimum number of pots that can be fished economically is ~60 pots, so any reduction in pot use should not apply below this number of pots. 138 13 Proposal 8: Implement more drastic reductions in pot use rates during the northern whale migration (i.e. May – July).

Comment: With greater entanglement of humpback whales in lobster fishing gear during the northern migration of humpback whales, it was discussed in terms of changing pot use rates throughout the season. Current Arrangements: The use of more than one pot per row is permitted, however anglers' eligibility is based on the number of pots they are allowed to use, not the number of vertical lines. Comment: Currently license holders are limited in terms of the number of vessels they can fish with based on their entitlement.

However, entanglements in lobster gear occur in the line, so the main goal should be to reduce the number of lines. If there is a drastic reduction in pot use, it may be economical for some anglers to fish more than one pot per line. Current arrangements: Articles 26A-(1) of the Plan; This clause applies to the use of pot lines and float devices used for lobster fishing during the period commencing on 1 May and ending on 31 October of any year.

Current arrangements: Fishermen are legally required to report interactions with protected species, but not sightings. Current Arrangements: Fishermen are not obligated to stay with an entangled whale they encounter. Current arrangements: There are currently no spatial closures of fisheries for the purpose of mitigating whale entanglement.

Workshop Outcomes

Low Impact Options

Moderate Impact Options

High Impact Options

Implementation of Options

Potential Research Projects

  • Spatial Distribution of Migrating Humpback Whales
  • Population Estimates of Breeding Stock D Humpback Whales
  • Entanglement Dynamics
  • Technical Innovation for Large Whale Disentanglement
  • Float Transmitters
  • Applicability of Sunken Head Gear for the WCRLMF
  • Increased Efficiency Through Pot Design

This will help reduce the financial burden of lost pots that may have been moved. It will also provide the ability to track complex whales that may not require the attachment of a tracking buoy. Submerged head rigging (where the trail line and floating platform are completely submerged) has been shown to be an effective strategy for mitigating whale entanglements.

This option was proposed by industry in 2013 (Lunow et al. 2013), although testing revealed that it is an expensive and impractical mitigation measure for the lobster fishery (How et al. 2015). However, workshop participants suggested revisiting this option to see if technological advances have been made possible. This technology is being implemented in other fisheries (eg Dungeness crab, California) to address the issue of whale entanglements.

Between May and October, there were suggestions for a possible further reduction in the rate of pot use (moderating impact options #1). As use rates are reduced, economic efficiency decreases, and at very low use rates the fishery may become uneconomic. This could be overcome by changes to the way usage rates are defined (ie maximum ropes instead of pots).

Alternative seine designs could be developed which have a greater fishing efficiency than the current regulated seines. Therefore, with a more efficient line, it can be economically profitable to continue fishing during periods of significantly reduced line (or line) consumption.

Acknowledgement

Appendices

  • Appendix 1 – Current Management Arrangements
    • Definitions
    • Applicable Clauses
  • Appendix 2 – Agenda
  • Appendix 3 – Participants
  • Appendix 4 – Presentation by Jason How
  • Appendix 5 – Presentation by John Edwards
  • Appendix 6 – Presentation by Todd A’Vard
  • Appendix 7 – Presentation by Jason How and Graeme Baudains

13:30 Whale entanglement – ​​state of knowledge Jason How (DPIRD) 14:15 Developments – challenges and risks John Edwards (DBCA) 14:45 Lunch.

Figure

Table 1 Summary of gear modification requirements for maximum rope length, surface rope,  floats and float rig length and periods between pulling pots for both shallow and deep  water
Figure 1 Diagrammatic representation of the gear modifications required in a) shallow (~&lt;

References

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