Tasmanian Octopus Fishery Assessment 2014/15
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TASMANIAN OCTOPUS FISHERY ASSESSMENT 2014/15 Timothy Emery and Klaas Hartmann February 2016 TASMANIAN OCTOPUS FISHERY ASSESSMENT 2014/15 Timothy Emery and Klaas Hartmann February 2016 This assessment of the Tasmanian Octopus Fishery is produced by the Institute for Marine and Antarctic Studies (IMAS). ISBN: 9781862958142 IMAS Fisheries Aquaculture and Coasts Private Bag 49 Hobart TAS 7001 Australia Email [email protected] Ph: 03 6227 7284, +61 3 6227 7284 (international) Fax: 03 6227 8035 The authors do not warrant that the information in this document is free from errors or omissions. The authors do not accept any form of liability, be it contractual, tortious, or otherwise, for the contents of this document or for any consequences arising from its use or any reliance placed upon it. The information, opinions and advice contained in this document may not relate, or be relevant, to a reader’s particular circumstance. Opinions expressed by the authors are the individual opinions expressed by those persons and are not necessarily those of the Institute for Marine and Antarctic Studies (IMAS) or the University of Tasmania (UTAS). © Institute for Marine and Antarctic Studies, University of Tasmania 2016 Copyright protects this publication. Except for purposes permitted by the Copyright Act, reproduction by whatever means is prohibited without the prior written permission of the Institute for Marine and Antarctic Studies. Contents Executive Summary ................................................................................ 5 1. Introduction ...................................................................................... 7 The fishery ................................................................................................................. 7 Assessment of stock status ................................................................................... 10 Stock status definitions ................................................................................................. 10 Proposed performance indicators and reference points............................................. 10 Data sources and analysis ..................................................................................... 11 Commercial data ............................................................................................................ 11 Recreational fishery ....................................................................................................... 11 Data analysis .................................................................................................................. 11 Species biological summaries ...................................................................................... 12 2. State catch, effort and catch rates ................................................ 15 Commercial catch from octopus pots ................................................................... 15 Influence of soak time .................................................................................................... 15 Catch and effort .............................................................................................................. 15 CPUE ............................................................................................................................... 17 Commercial catch from other fishing methods .................................................... 19 Recreational catch .................................................................................................. 20 3. Fine-scale catch, effort and catch rates ....................................... 21 4. Stock status ................................................................................... 24 5. Bycatch and protected species interaction ................................. 25 Acknowledgements ............................................................................... 26 References ............................................................................................. 26 IMAS Fishery Assessment Report Page 4 Executive Summary STOCK STATUS TRANSITIONAL-DEPLETING There has been an ongoing decrease in Octopus pallidus CPUE from 2005/06 to the lowest level in 2011/12 where it remained in 2012/13 and 2013/14. This long term trend indicates that the associated level of effort is likely to ultimately result in overfishing. In 2014/15 CPUE increased, however the associated level of effort was at or above that historically linked with depleting the stock. It is possible that this increase is at least partly due to the highly stochastic nature of Octopus pallidus and a shift in effort to areas with higher CPUE. Octopus pallidus is therefore classified as transitional depleting. STOCK Tasmanian Octopus Fishery INDICATORS Catch, effort and CPUE trends The Tasmanian Octopus Fishery is a multi-species fishery in the Bass Strait primarily targeting Octopus pallidus and the less abundant Octopus tetricus (Table 1). The Scalefish Fishery Management Plan (revised in 2009) provides the management framework for the fishery. The (commercial) fishery is effectively a sole operator fishery with the same operator since its commencement in 1980. This arrangement is effective in ensuring profitability in the fishery and stewardship of the resource. In this assessment, the octopus fishery is described in terms of catch, effort and catch rates at the State level. A more detailed analysis of catch, effort and catch rates at the fishing block level is also presented. The commercial catch history for the period 2000/01 to 2014/15 is assessed. Catches have increased over the last decade and have fluctuated at around 85 tonnes since 2005/06. While fishing effort fluctuated around 300,000 potlifts for almost a decade, it increased to over 400,000 potlifts in 2012/13 and 2013/14 before declining to 342,000 potlifts in 2014/15, which was more consistent with the long-term average. Historically there have been strong seasonal patterns in catch per unit effort (CPUE), with CPUE highest during the brooding peak for the species (autumn). While CPUE was higher in the summer months during 2013/14, the 2014/15 season was more reflective of the norm. CPUE has declined since the recent peak in the mid-2000s and prior to the latest season had been at similar levels to those experienced in the early 2000s, which corresponded to a lower level of harvest. In the 2014/15 season, both the 50-pot sample and logbook data indicated an increase in CPUE in both number and weight respectively. The stochastic nature of CPUE over the last decade is reflective of the biology of the species, which is inherently linked to environmental conditions making it difficult to assess the state of the stock and impact of fishing mortality. Relative to the 2013/14 season, catch and effort increased in areas east of King Island (3D3 and 3D4) and within inshore waters off Stanley (4E3) but declined in areas offshore of Stanley (4E1). Fishers continue to respond to changes in CPUE by shifting effort (and therefore catch) from areas with lower CPUE to areas with higher CPUE. Bycatch of octopus from other commercial fisheries (mainly Octopus maorum from the rock lobster fishery) have decreased over time and have been relatively low over the last five years (around 8 tonnes on average). The recreational catch of octopus appears minimal with around IMAS Fishery Assessment Report Page 5 a tonne retained per annum. The impact of the fishery on bycatch and protected species is low due to the nature of the gear used (i.e. unbaited pots). The ongoing decrease in Octopus pallidus CPUE since 2005/06 suggests that the associated level of effort is too high and likely to ultimately result in overfishing. While CPUE increased in 2014/15 it remains below the reference year and fishing effort is still at or above that historically linked with depleting the stock. It is possible that the increase in CPUE is at least partly due to the highly stochastic nature of Octopus pallidus and a shift in effort to areas with higher CPUE. Fishing effort remains concentrated in the most productive areas or those close to port, which given the substantial stock structure within Octopus pallidus increases the potential for recruitment overfishing. A cap or effective limit on spatial fishing effort could improve the probability that CPUE would increase in the future and ensure that the composition and recruitment potential of Octopus pallidus is not impacted by concentrated fishing effort. IMAS Fishery Assessment Report Page 6 1. Introduction The fishery The Tasmanian Octopus Fishery has been operating since 1980. Prior to December 2009 the fishery operated under permit. Historically, access to the commercial fishery was provided to holders of a fishing licence (personal), a vessel licence and a scalefish or rock lobster licence via a trip limit of 100 kg. This limit also applies to recreational fishers. Since December 2009, a specific octopus licence was required to participate in the fishery. Two licenses were issued, belonging to the same operator. Since 1996, under the Offshore Constitutional Settlement (OCS) with the Commonwealth of Australia, Tasmania has assumed management control of the octopus fishery out to 200 nautical miles. The Tasmanian Octopus Fishery primarily targets the pale octopus (Octopus pallidus), with lesser targeted catches of the Gloomy octopus (Octopus tetricus) and the Maori octopus (Octopus maorum) also taken, primarily as byproduct. The main fishing method is unbaited moulded plastic pots (volume