Ocean and Coastal Management 157 (2018) 9–22

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Ocean and Coastal Management

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A preliminary study on ABC estimation approach for ecosystem-based TAC T management

∗ Hee Joong Kanga, Young Il Seoa, Chang Ik Zhangb, a National Institute of Fisheries Science, 216, Gijanghaean-ro, Gijang-eup, Gijang-gun, Busan, Republic of Korea b Pukyong National University, 45, Yongso-ro, Nam-gu, Busan, Republic of Korea

ARTICLE INFO ABSTRACT

Keywords: Korea's acceptable biological catch (ABC) for total allowable catch (TAC) management has been estimated by a Ecosystem-based fisheries assessment five-tier system that relies on population-based stock assessment models according to available ecological in- Acceptable biological catch formation for pelagic or demersal . To overcome the limitations of the current ABC estimation system Total allowable catch based on population dynamic models, this study attempted to integrate the ecosystem-based fisheries assessment Species risk index (EBFA) approach into Korea's current ABC estimation system, and has developed an ABC estimation approach for Sustainability ecosystem-based TAC management. To estimate an ecosystem-based ABC, ABC estimated by the current ABC estimation system was adjusted depending on the species risk index (SRI) that was derived from risk analysis of EBFA. During the process, the SRI-F relationship which generalizes the relationship between SRI and fishing mortality (F) was devised, and was used to estimate an ecosystem-based ABC. Also, the SRI projection as a function of the F scenario was conducted to estimate the regression coefficient of a relationship of SRI and F. We demonstrated an ecosystem-based ABC estimation by applying it to the chub mackerel, one of the TAC species in Korea's large purse seine fishery. As a result, the F at ABC (0.39/year) was adjusted as 0.365/year, while ABC (180,000 mt) was reduced to 170,393 mt. We found that this approach can be used to conservatively estimate the TAC in an ecosystem-based context for quota-managed fisheries.

1. Introduction managed by an ecosystem-based approach considering the impact of fisheries on the ecosystem, to conserve and recover fishery resources Since 1998, the Korean government has implemented a total al- (Zhang, 2006). lowable catch (TAC)-based fisheries management system in order to In response to need for an ecosystem approach to fisheries, a lot of achieve sustainable fisheries. Currently, TAC-based management has fisheries organizations and countries have developed and introduced an been applied to eleven species: chub mackerel (Scomber japonicus), jack ecosystem-based approaches (CSIRO, 2005; FAO, 2007; MSC, 2009). mackerel (Trachurus japonicus), sailfin sandfish (Arctoscopus japonicus), Especially, an ecosystem-based fisheries assessment (EBFA) approach mottled ( pulchra), snow (Chionoecetes opilio), red snow was developed in Korea (Zhang et al., 2009). This method assesses crab (Chionoecetes japonicus), blue crab (Portunus trituberculatus), purple ecosystems by risk analysis of indicators to achieve four management Washington clam (Saxidomus purpuratus), pen shell (Atrina pectinata), objectives: sustainability, biodiversity, habitat quality, and socio-eco- spiny top shell (Batillus cornutus), and common squid (Todarodes paci- nomic benefit(Zhang et al., 2009, 2010). Furthermore, many EBFA ficus). The TAC for these has been allocated based on acceptable bio- application studies have been conducted on Korean fisheries (Seo, logical catch (ABC). The ABC for Korean TAC management has been 2011; Yoon, 2014; Lee, 2014), In particular, a fishery resources as- estimated by a five-tier system that relies on population-based stock sessment, also a forecasting and management system named “an in- assessment models according to available ecological information for tegrated fisheries risk analysis method for ecosystems (IFRAME)”, was pelagic or demersal species (Fig. 1). developed based on EBFA (Zhang et al., 2011), and its usefulness in Korean fishery has been managed by TAC management and other assessing impacts of climate change on fisheries has been verified with measures, but has been degraded in quantity and quality due to eco- comparative analyses of ecosystem models (Hollowed et al., 2013). system changes caused by overfishing and marine pollution (Zhang and The purpose of this study is to integrate EBFA into the current ABC Lee, 2004). Therefore, Korean fishery resources had a need to be estimation system, and develop an new ABC estimation approach for

∗ Corresponding author. E-mail address: [email protected] (C.I. Zhang). https://doi.org/10.1016/j.ocecoaman.2018.02.006 Received 13 September 2017; Received in revised form 22 January 2018; Accepted 10 February 2018 0964-5691/ © 2018 Elsevier Ltd. All rights reserved. H.J. Kang et al. Ocean and Coastal Management 157 (2018) 9–22

Fig. 1. Current acceptable biological catch (ABC) estimation system for total allowable catch (TAC) management in Korea (white rectangle: input data; yellow parallelogram: population parameters; blue rounded rectangle: estimates; light green rectangle: estimates for management; modified from Zhang and Lee (2001)). (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.) ecosystem-based TAC management. To estimate an ecosystem-based objective risk index (ORI), and species risk index (SRI) are estimated in ABC, We adjusted ABC calculated by the current ABC estimation system sequence, and the current ABC is adjusted according to SRI level into depending on the species risk index (SRI), which was derived from risk the new ABC estimation. analysis of EBFA. During the process, the SRI-F relationship which The ABC adjustment process for ecosystem-based ABC estimation is generalizes the relationship between SRI and the instantaneous rate of shown in Fig. 3. The first step is estimation of the SRI. When ABC was fishing mortality (F) was devised and was used to estimate an eco- estimated by tier 1–3 methods through the current ABC estimation system-based ABC. Also, SRI projection as a function of the F scenario system, considering information levels, SRI was estimated by E-tier 1, was conducted to estimate the regression coefficient of the SRI-F re- quantitative analysis, with EBFA needing sufficient information about lationship. The new ecosystem-based ABC estimation system was de- the ecosystem. Additionally, in situations where value of fishing mor- monstrated by applying it to the chub mackerel, one of the TAC species tality is known, SRI can be simply obtained through the SRI-F re- in Korea's large purse seine fishery. lationship which will be introduced in the next step. On the other hand, When ABC was estimated by tier 4–5 methods through the current ABC 2. Materials and methods estimation system, SRI was estimated by E-tier 2, semi-quantitative or qualitative analysis, with EBFA needing a relatively low level of in- 2.1. Ecosystem-based ABC estimation system formation about the ecosystem. The second step is projection of the SRI as a function of the in- EBFA is a pragmatic ecosystem-based approach for assessing fishery stantaneous rate of fishing mortality (F) scenario. This study general- resources in Korean waters involving four management objectives: ized the relationship between SRI and F, and developed the SRI-F re- sustainability, biodiversity, habitat quality, and socio-economic benefit lationship. It also predicted values of indicators and then calculated RS, (Zhang et al., 2009, 2010). The new ecosystem-based ABC estimation ORI, and SRI in sequence. Finally, the SRI-F relationship's regression system was developed in the study by incorporating EBFA into the coefficient was estimated by a linear regression analysis of SRI by F. current ABC estimation system in Korea. Fig. 2 shows a simple diagram However, when ABC was estimated by tier 4–5 methods through the for the new ecosystem-based ABC estimation system. This system uti- current ABC estimation system, this step was skipped. lizes input data of the current ABC estimation system as data of in- The third step is projection of an ecosystem-based ABC (ABCEBFA) dicators for sustainability. In addition to this, data of indicators for when SRI varies. Substituting the regression coefficient β of the SRI-F biodiversity, habitat quality, and socio-economic benefit are required. relationship into the ABCEBFA estimation equation, this study projected From the indicators for each management objective, risk score (RS), changes of ABCEBFA as a function of SRI. In the preceding process, an

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