Estimation of Population Dynamic Parameters of Longtail Tuna, Thunnus tonggol (Bleeker, 1851) around the Lombok Seas, West Nusa Tenggara.

Pi:I Nyoman Giri Putra,
Institution: Faculty of Marine Science, Udayana University, Kampus Bukit Jimbaran, Bali

Project Overview:
Indonesia is the largest tuna producer in Southeast Asia with total production reaching 1,362.9 metric tons with trade value reaching 972.4 million US dollars (SEAFDEC, 2014). According to the Ministry of Marine Affairs and Fisheries, tuna production in Indonesia are increased by 10% within 2009-2014 (KKP, 2015. However, assessments of the Indonesian tuna fisheries showed that the populations are in fully exploited and overexploited status (Widodo et al., 2003). Regarding to this cases, some conservation plans are proposed to recovering the stocks. Unfortunately, stocks assessment and conservation management in present day are currently focus on highly migrating and sharing stocks tuna such as yellowfin (Thunnus albacares), bigeye (T. obesus), albacore (T. alalunga), skipjack (Katsuwonus pelamis) and southern bluefin (T. maccoyii) with little emphasis on neritic tuna.

Globally, the trend of longtail tuna fishing continues to increase from 100,000 tons in 1985 to 204,259 tons in 2014 (FAO, 2018). Although the trend of catching up is increasing, the number of catches each year fluctuates and this is an indication that the longtail tuna fishery conditions are less stable. Over exploitation would risk the sustainability of this species in nature because the species is slow growing (Griffiths et al. 2010) and relatively lack of genetic structures (Kunal et al., 2014).

The growing commercial of this species, the enhanced exploitation rate and lack of data on stock structure warrant the need for an extensive study to investigate the population dynamics of longtail tuna. Determination of tuna population dynamics is essential to support resource recovery, predicting future ecological impacts as populations change, forecasting economic impacts to the fishing and seafood industry and to aid in delineating and monitoring populations for fishery management. Therefore, this project aim to estimate some population dynamics parameters of longtail tuna such as length-weight relationships, length frequency distribution, and prediction of maximum length. This project will be based at three traditional markets located in Lombok, West Nusa Tenggara named Tanjung Luar, Labuhan Lombok, and Teluk Awang. Activities during this project including the measurement of the length and weight of longtail tuna, tissue collections, data analysis, research dissemination and publication.