Biology, fishery, conservation and management of Indian Ocean tuna fisheries

Abstract

− The focus of the study is to explore the recent trend of the world tuna fishery with special reference to the Indian Ocean tuna fisheries and its conservation and sustainable management. In the Indian Ocean, tuna catches have increased rapidly from about 179959 t in 1980 to about 832246 t in 1995. They have continued to increase up to 2005; the catch that year was 1201465 t, forming about 26% of the world catch. Since 2006 onwards there has been a decline in the volume of catches and in 2008 the catch was only 913625 t. The Principal species caught in the Indian Ocean are skipjack and yellowfin. Western Indian Ocean contributed 78.2% and eastern Indian Ocean 21.8% of the total tuna production from the Indian Ocean. The Indian Ocean stock is currently overfished and IOTC has made some recommendations for management regulations aimed at sustaining the tuna stock. Fishing operations can cause ecological impacts of different types: by catches, damage of the habitat, mortalities caused by lost or discarded gear, pollution, generation of marine debris, etc. Periodic reassessment of the tuna potential is also required with adequate inputs from exploratory surveys as well as commercial landings and this may prevent any unsustainable trends in the development of the tuna fishing industry in the Indian Ocean.

The role of indigenous knowledge in the management of marine resources: a case study of Kuruwitu and Mkunguni fishing areas in Kenya

“…Indigenous knowledge of seasonality is critical since it influences the timing in species availability and consequently fishing patterns ( Johannes et al, 2000). The results on tuna abundance revealed in this study concur with those of a study by Gopalakrishna et al (2012) which allude to the fact that tuna may be caught throughout the year but are generally a seasonal species.…”

Feeding Habits of Bigeye Tuna (Thunnus obesus) in the Western Indian Ocean Reveal a Size-Related Shift in Its Fine-Scale Piscivorous Diet

“…As an economically valuable species, bigeye tuna has been caught using industrial purse seine and longline fisheries in the past and using gillnet fisheries in the Indian Ocean in recent years. Landings peaked in the late 1990s before diminishing across all oceans (Nootmorn, 2004;IOTC, 2005;Pillai and Satheeshkumar, 2012). The International Union for Conservation of Nature Red List of Threatened Species classifies bigeye tuna as a vulnerable species, indicating that ensuring a theoretically optimal catch is essential.…”

Composition and diversity of larval fish in the Indian Ocean using morphological and molecular methods

“…Pielou's evenness index, J' (2; Pielou 1975) was used to study the equality of families for each station and study region, where H′ is the calculated Shannon-Weaver diversity index value and S is the total number of species.…”