Second-guessing uncertainty: Scenario planning for management of the Indian Ocean tuna purse seine fishery

Abstract

a b s t r a c tAn important task of natural resource management is deciding amongst alternative policy options, including how interventions will affect the dynamics of resource exploitation. Yet predicting the behaviour of natural resource users in complex, changeable systems presents a significant challenge for managers. Scenario planning, which involves thinking creatively about how a socio-ecological system might develop under a set of possible futures, was used to explore uncertainties in the future of the Indian Ocean tuna purse seine fishery. This exercise stimulated thinking on how key social, economic and environmental conditions that influence fleet behaviour may change in the future, and how these changes might affect the dynamics of fishing effort. Three storylines were explored: an increase in marine protection, growing consumer preference for sustainable seafood, and depletion of tuna stocks. Comparing across several possible future scenarios, a number of critical aspects of fleet behaviour were identified that should be important considerations for fishery managers, but which are currently poorly understood. These included a switch in fishing practices, reallocation of effort in space, investment in new vessels and exit from the fishery. Recommendations for future management interventions in the Indian Ocean were offered, along with suggestions for research needed to reduce management uncertainty.

Embracing uncertainty in applied ecology

“…Scenario analysis is a good way to structure thinking about the future in a way that encourages the contemplation of uncertainties and their potential implications. This has been widely used in climate science, but is uncommon in applied ecology; one example is Davies, Mees & Milner‐Gulland's () analysis of likely futures for the Indian Ocean tuna fishery.…”

Kerentanan Perikanan Bycatcth Tuna dari Samudera Hindia: Evidance dari Pelabuhan Perikanan Pelabuhanratu

“…Little tuna dan albacores di Indian Ocean panjang maksimum mencapai 240 cm, koefisien tumbuh 0,3, umur maksimum 6,5 tahun, umur mulai matang gonad 2,4 tahun, dan panjang saat matang gonad 56 cm (Fredou et al 2016). Yellowfin tuna tumbuh lebih lambat, umur mencapai 10 tahun dan mulai matang sexual 2,8 tahun dan dan memijah sepanjang tahun (Davies et al 2015). Fekunditas T albacores lebih tinggi dari little tuna yang fekunditas berkisar 17.814-560.792 butir telur dengan rata-rata 109.807 butir (Ardelia et al 2016).…”

“…Tingkat kematian adalah 0,72, dengan persentase rekruitmen diperoleh sebesar 22,66, dan pertama kali memijah pada umur sekitar 1,3 tahun. Skipjack tuna hidup sampai 4-5 tahun, tumbuh cepat, mencapai matang gonad pada umur 1,8 tahun dan memijah sepanjang tahun (Davies et al, 2015). Skipjack dominan tertangkap dengan purse seine (38%), gillnet (36%), pole and line 17% dan lainnya 9% (Davies et al, 2015).…”

“…Rogan and Mackey (2007) mencatat bahwa di NE Atlantic kelompok megafauna juga banyak tertangkap selain skipjack, baby tuna dan lemadang. Perikanan tuna yang menggunakan alat tangkap purse seine sebagian besar menangkap kelompok ikan yang schooling spesies skipjack (Katsuwonus pelamis), yellowfin (Thunnus albacares) dan big eye tuna (Davies et al 2015). Perikanan artisanal dapat menangkap ikan ini karena tidak secepat high migratory lainnya (Belhabib et al 2016).…”

“…Peningkatan vulnerability skipjack dipengaruhi musiman dan beberapa factor lingkungan seperti kedalaman dan termoklin (Andrade et al, 2004). Jenis yellowfin, skipjack, dan big eye tuna berbeda level susceptabilitasnya, overfishing, variasi laju tumbuh, umur pada saat matang gonad, dan daerah pemijahan (Davies et al, 2015). Fredou et al (2017) Dalam praktek pengelolaan perikanan yang bertanggungjawab maka resiko kerentanan harus diturunkan.…”