Size-composition of Annual Landings in the White Shrimp, Litopenaeus setiferus, Fishery of the Northern Gulf of Mexico, 1960–2006: Its Trend and Relationships with Other Fishery-dependent Variable

The potential for growth overfishing in the white shrimp, Litopenaeus setiferus, fishery of the northern Gulf of Mexico appears to have been of limited concern to Federal or state shrimp management entities, following the cataclysmic drop in white shrimp abundance in the 1940’s. As expected from surplus production theory, a decrease in size of shrimp in the annual landings accompanies increasing fishing effort, and can eventually reduce the value of the landings. Growth overfishing can exacerbate such decline in value of the annual landings. We characterize trends in size-composition of annual landings and other annual fishery-dependent variables in this fishery to determine relationships between selected pairs of these variables and to determine whether growth overfishing occurred during 1960–2006. Signs of growth overfishing were equivocal. For example, as nominal fishing effort increased, the initially upward, decelerating trend in annual yield approached a local maximum in the 1980’s. However, an accelerating upward trend in yield followed as effort continued to increase. Yield then reached its highest point in the time series in 2006, as nominal fishing effort declined due to exogenous factors outside the control of shrimp fishery managers. The quadratic relationship between annual yield and nominal fishing effort exhibited a local maximum of 5.24(107) pounds (≈ MSY) at a nominal fishing effort level of 1.38(105) days fished. However, annual yield showed a continuous increase with decrease in size of shrimp in the landings. Annual inflation-adjusted ex-vessel value of the landings peaked in 1989, preceded by a peak in annual inflation-adjusted ex-vessel value per pound (i.e. price) in 1983. Changes in size composition of shrimp landings and their economic effects should be included among guidelines for future management of this white shrim

Status of demersal fishery resources in the Gulf of Thailand

Data from trawl surveys (1961 - 95) and annual production statistics (1971 - 95) were used to examine the status of demersal fishery resources in the Gulf of Thailand. Analyses were focused on biomass trends, population parameters and exploitation rates of dominant species, and assessment of excess capacity from fishing effort and yield estimates. The results indicate by 1995, the trawlable biomass in the Gulf had declined to only about 8.2% of the biomass level in 1961. The substantial decline is true for major components (demersal fish and trash fish) and species groups (Nemipterus spp., Priacanthus spp., Saurida spp. and squids) comprising trawlable biomass. Estimates of exploitation rate (E) for 23 species indicate that most (particularly demersals) are over-fished. By 1995, 21 of the species had E values of 0.79 and higher. Analyses of standardized fishing effort and yield using the Fox model indicate that the 1995 fishing effort was about twice the level needed to harvest the maximum sustainable yield. Overall, the results illustrate that the resources are severely over-exploited. The excess demersal fishing effort is estimated to be about 50% of the number of registered boats in 1995.Fishery resources, Demersal fisherie, Fishery surveys, Biomass, Population density, Shrimp fisheries, Catch/effort, ISEW, Thailand Gulf,

The Drama of Fishing Commons: Cournot-Nash Model and Cooperation

Cournot-Nash model; drama of the commons; cooperation; game theory; fishing effort.

The Analysis Of Fishing Effort By Scraping Net In Sungai Nyamuk, Sinaboi Sub District, Rokan Hilir Regency Of Riau Province

Research on the analysis of fishing effort by fishing scraping net, held in April2015 in Sungai Nyamuk, Sinaboi Sub District, Rokan Hilir Regency Of Riau Province.The research of aims to analyze large venture capital investments, and how large grossincome and net income of using fishing scraping net. The method used is a surveymethod. Determination respondents stratification of random sampling performed usinga method that is done by looking at the motor boat scraping levels at the study siteconsisting of a motor boat with a cargo scraping net 0,7 GT and GT 1. Respondentswere drawn consists of a fishing effort using the tool catches scraping net to charge 1GT by 3 fishermen and fishermen scraping net 0,7 GT by 3 people.The total investments invested in doing scraping net fishermen fishing effort is Rp29.647.000, for a motor boat fishermen 0,7 GT and Rp 44.295.000 for boat motors 1GT. Gross income of scraping net fishermen for season of motor boat 0,7 GT Rp.305.000 of day and Rp. 109.000 for not season of day. For motor boat 1 GT Rp.385.000 for season of day and Rp. 183.000. Net income scraping net fishermen of 0,7GT Rp. 196.000 for season of day and not net income for not season of day. As forfishermen of motor boat 1 GT is Rp. 220.000 for season of day and Rp. 18.000 for notseason of day

TIME, CAPITAL INTENSITY, AND THE COST OF FISHING EFFORT

The notion that a fishing vessel's costs are a function of its "effort" is a useful paradigm in fishery analysis. This paper elaborates on this micro theoretic approach, and proposes a way to view the cost of effort relation as the interaction of capital intensity decisions and the length of the fishing season. The model indicates that capital intensity decisions are affected by season closures, and that season closures can be used to redistribute wealth among different classes of fishermen.Production Economics, Resource /Energy Economics and Policy,

Mapping Fishing Effort through AIS Data

Several research initiatives have been undertaken to map fishing effort at high spatial resolution using the Vessel Monitoring System (VMS). An alternative to the VMS is represented by the Automatic Identification System (AIS), which in the EU became compulsory in May 2014 for all fishing vessels of length above 15 meters. The aim of this paper is to assess the uptake of the AIS in the EU fishing fleet and the feasibility of producing a map of fishing effort with high spatial and temporal resolution at European scale. After analysing a large AIS dataset for the period January-August 2014 and covering most of the EU waters, we show that AIS was adopted by around 75% of EU fishing vessels above 15 meters of length. Using the Swedish fleet as a case study, we developed a method to identify fishing activity based on the analysis of individual vessels’ speed profiles and produce a high resolution map of fishing effort based on AIS data. The method was validated using detailed logbook data and proved to be sufficiently accurate and computationally efficient to identify fishing grounds and effort in the case of trawlers, which represent the largest portion of the EU fishing fleet above 15 meters of length. Issues still to be addressed before extending the exercise to the entire EU fleet are the assessment of coverage levels of the AIS data for all EU waters and the identification of fishing activity in the case of vessels other than trawlers.JRC.G.3-Maritime affair

Environmental and fishing effects on the dynamic of brown tiger prawn (Penaeus esculentus) in Moreton Bay (Australia)

This analysis of the variations of brown tiger prawn (Penaeus esculentus) catch in the Moreton Bay multispecies trawl fishery estimated catchability using a delay difference model. It integrated several factors responsible for variations in catchability: targeting of fishing effort, increasing fishing power and changing availability. An analysis of covariance was used to define fishing events targeted at brown tiger prawns. A general linear model estimated inter-annual variations of fishing power. Temperature induced changes in prawn behaviour played an important role in the dynamic of this fishery. Maximum likelihood estimates of targeted catchability ($3.92 \pm 0.40 \ 10^{-4}$ boat-days$^{-1}$) were twice as large as non-targeted catchability ($1.91 \pm 0.24 \ 10^{-4}$ boat-days$^{-1}$). The causes of recent decline in fishing effort in this fishery were discussed.Comment: revised manuscript following reviewers comments + adding data and code for reader