Fishery, biology and stock structure of skipjack tuna, Katsuwonus pelamis (Linnaeus, 1758) exploited from Indian waters

Global catches of skipjack tuna have been steadily increasing since 1951, reaching a peak in 2009 at 25, 99,681 t (Fig.1). Most of the catches were reported from the fishing areas 71, 51, 61 and 34 (FA0, 2011). Globally skipjack tuna is caught at the surface, mostly with purse seines and pole and lines and to a small extent by gillnets, troll lines and longlines. Gears like purse-seine and very long gillnets enabled few nations to augment their production, whereas traditional pole and line nations suffered heavily

Different methods for standardization of fishing efforts

Surplus production models are widely employed to evaluate the condition of fish stocks, encompassing the entire stock, overall fishing effort, and the total yield derived from the stock. These models operate under the assumption that variations in population biomass result from hikes due to growth and reproduction, as well as drops due to natural and fishing mortality. Utilizing Catch-Per-Unit-Effort (CPUE) as input, these models rely on the presumption that CPUE is directly proportional to the biomass of fish stock in the sea. An inherent challenge in fitting such a production model lies in determining CPUE, whether in terms of units operated or in hours of operation/actual fishing hours (AFH) or in any measure of fishing efforts. Given the heterogeneous nature of fishing fleets in tropical regions, they are often categorized into boat-gear categories, where fishing units within each category share similar characteristics and performance. When assessing the collective impact of the fishing operations of the entire fleet on the exploitation of fish stock, nominal addition of the efforts of different boat-gear categories may lack meaningfulness without prior effort adjustment to enhance comparability. In tropical regions, due to the varying capacities of gears and the potential presence of multiple species in each gear, the effort expended to catch a resource cannot be simply considered as the sum of the duration/units of operation of all gears. This paper aims to underscore various effort standardization methodologies found in the literature for different situations, offering insights into the challenges faced in tropical fisheries and proposing a way forward

Passive georeferencing: A promising approach for finding probable fishing grounds

Fishery management can benefit greatly from the use of geographic information system tools for habitat mapping, georeferencing fish catch and fishing effort data, and linking catch to oceanographic and biochemical parameters. As exploratory fishery resource surveys are time-consuming and expensive, landing centre-based surveys are frequently used in India to estimate the marine fishery resources. But it is challenging to map the habitat of the resources in such surveys as the resources seen at the landing centre are not geo-tagged. Passive georeferencing refers to the process of determining the geographical location of an object or entity using external information without actively transmitting any signals and is useful in situations where active transmission may not be desirable or feasible, and it allows for effective tracking and positioning without relying on active participation from the object being located. In this paper, the application of passive georeferencing approach for finding probable fishing grounds has been discussed along with its pros and cons and concluded with the way forward

Renaissance in Fisheries: Outlook and Strategies - Book of Abstracts 9th Indian Fisheries Forum, December 19-23, 2011, Chennai, India

The Asian Fisheries Society – Indian Branch (AFSIB) since its inception in 1986, has been providing a platform for discussion at the national level on issues related to research, development, education and policies by organizing Indian Fisheries Forum (IFF) every three years in different parts of the country. The 9th Indian Fisheries Forum (9th iff) will be hosted by the Central Marine Fisheries Research Institute (CMFRI), at Chennai during 19-23 December 2011. The main theme of the 9th iff is “Renaissance in Fisheries: Outlook & Strategies”. It would have a comprehensive look for the fisheries and aquaculture sectors, for achieving greater synergy among the stakeholders and planning strategies for capture fisheries and aquafarming to build higher levels of sustainability and profitability. The forum would also address the issues of impact of climate change and its mitigation, resource constraint and species diversification for the expansion of fish production activity; and encourage young scientists to undertake need-based and resource specific research. An international symposium sponsored by the Bay of Bengal Large Marine Ecosystem (BoBLME) is scheduled to be held during the forum on 21 December, 2011 with theme: Bay of Bengal–Ecosystem Approach to Fisheries Management

Determining target species for assessment in multispecies and multigear fisheries: insights from an expanded CMFRI-NMFDC database

This paper highlights the richness of information available in an expanded ICAR-CMFRI-NMFDC fish catch and effort database for the state of Kerala. Strengthening of the database by digitizing data in the old paper data sheets was done under a multi-national project, ICAR-CMFRI-CSIRO-LENFEST Ocean Programme. The high diversity of fished taxa was classified according to the periodicity of its occurrence over this long period. Guidelines for determining the number of species for which stock assessment is to be carried out in the context of a multigear and multispecies fisheries sector were derived. This national-level database will be of immense use to researchers and policy makers for preparing fisheries management plans for the sustainable harvest of marine fishery resources

Overfishing and Climate Drives Changes in Biology and Recruitment of the Indian Oil Sardine Sardinella longiceps in Southeastern Arabian Sea

The recent fluctuations in abundance of the Indian oil sardine Sardinella longiceps, a tropical small pelagic clupeid fish, was investigated in the light of overfishing and variations in its habitat ecology in southeastern Arabian Sea. In 2012, its landings peaked to an all-time record making it the fifth largest sardine fishery in the world, and within 3 years the catches were reduced to nearly a tenth of that level. This study examined the fishery dependant factors such as effort, catch rates and expansion of fishing area; the biological variations in fish size, maturity and recruitment; and tried to relate this to the environmental variations in the sardine habitat and food availability. The 2012 mega harvest was a result of a 2-time increase in gear size and engine capacity of fishing crafts and a 3.7-time increase in fishing effort. The female maturation process was strongly influenced primarily by rainfall and then by upwelling and the resulting influx of cold nutrient-rich water in the habitat from April much before the start of the monsoon in June. After 2013, the weak monsoons and the 2015 El Nino Southern Oscillation resulted in a warmer (by an average of 1.1°C) period which negatively impacted the maturation process. The abundance of jellyfishes which are larval and young fish predators in the habitat negatively affected recruitment after 2013. The mismatch in timing of phytoplankton productivity and sardine larvae in the habitat also affected the recruitment success. These environmental divergences coupled with the excessive capture (beyond maximum sustainable yields) of spawning stock and juveniles from 2010 has resulted in this biological catastrophe which has affected the livelihood of thousands of small-scale fishers. A more responsive fisheries administration with timely restriction on fishing effort and protection of spawning stocks by way of fishery closure would have helped minimize the impacts

Status of Indian marine fish stocks: modelling stock biomass dynamics in multigear fisheries

A biomass dynamics modelling study to derive biological reference points and management requirements of 223 commercially important fish stocks in different maritime states of India was conducted. Two decades (1997–2016) of fishery-related data on the harvest of resources by different types of fishing fleets formed the input. The multigear nature of the fishery situation was solved by introducing a gear standardization parameter into the biomass dynamics model. The relative positions of the fish stocks were depicted through Kobe plots generated for the ten maritime states/union territory, and the fish stocks were categorized, based on the status, into sustainable, overfished, recovering, and overfishing. The results indicate that 34.1% of the assessed fish stocks in the country are sustainable, 36.3% are overfished, 26.5% are recovering, and 3.1% are in the overfishing status. Regionally, the percentage of sustainable fish stocks were high along the southwest coast (51.6%), overfished stocks were high along the northwest coast (54.2%), and recovering fish stocks were high along the northeast coast (47.8%). The national mean B/BMSY was estimated as 0.86, which is a strong reason for strengthening fisheries management. Fishing fleets harvesting overfished stocks were examined for each maritime state, and recommendations regarding reduction in annual fishing hours are made

Appraisal of Marine Fisheries of Kerala

Kerala ranks first in marine fish production of India forming nearly 25% (avg. 5.75 lakh tonnes) of the total annual production. The annual export of marine products from the state yields to the nation a foreign exchange of Rs. 1100 crores. There has been spectacular growth in the marine fisheries sector of the state due to fisheries friendly government policies, well developed harvest and post harvest infrastructure and increased demand for sea food both in the domestic and export markets. Kerala has been in the forefront in absorbing innovative and new technologies in fishing practices, which has led marine fisheries to take a complex structure

Proceedings of the 5th International Symposium on Cage Aquaculture in Asia CAA5

Proceedings of the 5th International Symposium on Cage Aquaculture in Asia CAA