scholarly journals Fishing Effort and Associated Catch per Unit Effort for Small-Scale Fisheries in the Mozambique Channel Region: 1950–2016

2021 ◽  
Vol 8 ◽  
Author(s):  
Dirk Zeller ◽  
Gabriel M. S. Vianna ◽  
Matthew Ansell ◽  
Angie Coulter ◽  
Brittany Derrick ◽  
...  
Keyword(s):  
Fishing Effort ◽  
Small Scale ◽  
Catch Per Unit Effort ◽  
Important Species ◽  
Small Scale Fisheries ◽  
Mozambique Channel ◽  
Fishing Vessels ◽  
Unit Effort ◽  
Fishing Capacity ◽  
Channel Region

The Mozambique Channel region in East Africa has diverse marine ecosystems and serves as a migratory corridor for economically important species. Local and foreign industrial fisheries operate in the Mozambique Channel, but regional small-scale fisheries are the crucially important fisheries that provide food security, livelihoods, and economic opportunities for rural coastal communities. This study reconstructed and investigated trends in the fishing effort and catch per unit effort (CPUE) of small-scale marine fisheries in four Exclusive Economic Zones (EEZ) that constitute the Mozambique Channel, i.e., Union of Comoros, Madagascar, Mayotte, and Mozambique, from 1950 to 2016. Effective fishing effort for small-scale fisheries in the form of fishing capacity in kWdays (i.e., kilowatt days) was derived using the number, length, motorization (engine power) by fishing vessels, as well as an approximate human-powered equivalent for shore-based fishers without vessels, as well as days of fishing per year. Effective small-scale fishing effort in the Mozambique Channel increased by nearly 60 times from just over 386,000 kWdays in 1950 to over 23 million kWdays in 2016. Correspondingly, the overall small-scale CPUE, based on previously and independently reconstructed catch data declined by 91% in the region as a whole, from just under 175 kg⋅kWday–1 in the early 1950s to just over 15 kg⋅kWday–1 in recent years. All four EEZs showed the strongest declines in the small-scale CPUE in the earlier decades, driven by motorization and growth in vessel numbers impacting effective fishing effort. Increased motorization combined with a substantial growth in overall vessel numbers were the drivers of the increasing fishing effort and decreasing CPUE, and clearly suggest that continuing to increase the fishing capacity of small-scale fisheries in the absence of effective and restrictive management actions may exacerbate overexploitation risk.

scholarly journals Effects of selective fishing on a small scale multi-species and multi-gear freshwater fishery in the Magdalena River Basin (Colombia)

2021 ◽  
Author(s):  
Sandra Jeannette Hernández Barrero ◽  
Mauricio Valderrama Barco ◽  
Carlos Guillermo Barreto Reyes ◽  
Wolfgang B Stotz
Keyword(s):  
River Basin ◽  
Cost Benefit ◽  
Mesh Size ◽  
Fishing Effort ◽  
Trophic Levels ◽  
Self Control ◽  
Control Measures ◽  
Small Scale ◽  
Catch Per Unit Effort ◽  
Unit Effort

Classical management has not been able to stop the 65% decrease in fishery production during the last 40 years in the Magdalena-Cauca River Basin. To analyze the effects of selective fishing of multiple species and small scale fisheries we addressed temporal changes at fishing level and the response of fishermen. The fishery reduced production and CPUE (catch per unit effort standardized), decreased the large sizes and growth rates of Prochilodus magdalenae and Pseudoplatystoma magdaleniatum, changed the abundance of trophic levels (decreased carnivores and increase of detritivores, omnivores), and increased exploitation rates. The fishermen have responded by implementing self-control measures, diversifying fishing gear and mesh size, including new species and sizes in the catch with a higher cpue (catch per unit effort) of small sized fish, adjusting the fishing effort to the abundance. We conclude that selective fishing has had ecological effects and fishermen have empirically self-regulated to optimize the cost-benefit ratio of their activity, developing a fishery that is more in line with ecosystemic structures. We address the balanced harvest strategy as a management alternative.

Short-term decisions of small-scale fishers selecting alternative target species: a choice model

2004 ◽  
Vol 61 (3) ◽  
pp. 374-383 ◽  
Author(s):  
Silvia Salas ◽  
Ussif Rashid Sumaila ◽  
Tony Pitcher
Keyword(s):  
Resource Availability ◽  
Choice Model ◽  
Daily Basis ◽  
Discrete Choice Models ◽  
Fishing Effort ◽  
Small Scale ◽  
Target Species ◽  
Catch Per Unit Effort ◽  
Small Scale Fisheries ◽  
Management Policies

The complexity of small-scale fisheries makes it difficult to predict the allocation of fishing effort among alternative target species in mixed fisheries, resulting in limitation for fisheries management. One reason for the difficulty is that fishing effort has been assumed as an aggregate of different components, without consideration of fishers' decisions. In this paper, we use discrete choice models to identify factors involved in fishers' decisions about selecting target species on a daily basis. We analyze catch data, by species and fisher, from three fishing communities of Yucatan, Mexico, to contrast the following models: (i) random selection, (ii) economic motivation, and (iii) changes in resource availability. Our results show that fishers do not operate at random but consider information on resource availability and revenues generated from previous trips before selecting or shifting a target. We compare the results among communities and also use the proposed models to predict changes in fishing effort levels given changes in species price and catch per unit effort. We stress the importance of understanding fishers' behavior when it comes to developing appropriate management policies.

scholarly journals Catch per unit effort (CPUE) and catch composition of small scale fisheries in Gökova Bay

2015 ◽  
Vol 32 (3) ◽  
pp. 135-143
Author(s):  
Hakkı Dereli ◽  
Zafer Tosunoğlu ◽  
Huriye Göncüoğlu ◽  
Vahdet Ünal
Keyword(s):  
Small Scale ◽  
Catch Per Unit Effort ◽  
Small Scale Fisheries ◽  
Unit Effort ◽  
Catch Composition

scholarly journals Experimental evaluation of influence of FADs on community structure and fisheries in coastal Kenya

2018 ◽  
Vol 31 ◽  
pp. 6 ◽  
Author(s):  
Emmanuel K. Mbaru ◽  
Dorcas Sigana ◽  
Renison K. Ruwa ◽  
Elizabeth M. Mueni ◽  
Collins K. Ndoro ◽  
...  
Keyword(s):  
Fish Assemblages ◽  
Small Scale ◽  
Catch Per Unit Effort ◽  
Fish Stocks ◽  
Coastal Fisheries ◽  
Small Scale Fisheries ◽  
Open Sea ◽  
Catch Composition ◽  
Structural Indices ◽  
Fish Aggregating Devices

Fish aggregating devices (FADs) have been widely used by commercial fisheries to increase the catchability of pelagic stocks in the open sea. FADs have the potential to enhance nearshore small-scale fisheries where stocks are often overfished. This study examined changes in catch composition, abundance, catch and effort, and aspects of diversity in Kenya's nearshore coastal fisheries after deployment of anchored fish aggregating devices (AFADs). The study combined both fishery independent and dependent methods in assessing changes in fish assemblages post-deployment. Results showed orders of magnitude increase in length, weight, commercial value, and catch per unit effort (CPUE) of landed catch after deployment of FADs suggesting that FADs had a positive effect on the local fishery. Species richness at FAD sites increased post-deployment (n = 281) compared to pre-deployment values (n = 223). Simultaneous use of several complementary structural indices may be required in order to accurately describe and monitor fish assemblages around the FADs. The findings suggest that AFADs are capable of creating both short and long-term impacts on livelihoods, with the potential to deflect pressure on the overfished nearshore fish stocks. However, more research will be needed on redistribution of fish around FADs, design and placement configuration, and site selection amongst others.

scholarly journals A Bio-Economic Analysis of the Liberian Coastal Fisheries

2020 ◽  
Vol 12 (23) ◽  
pp. 9848
Author(s):  
Alvin Slewion Jueseah ◽  
Dadi Mar Kristofersson ◽  
Tumi Tómasson ◽  
Ogmundur Knutsson
Keyword(s):  
New Technologies ◽  
Fishing Effort ◽  
Small Scale ◽  
Exclusion Zone ◽  
Coastal Fisheries ◽  
Small Scale Fisheries ◽  
Species Complexes ◽  
Limited Enforcement ◽  
Dugout Canoes ◽  
The Government

Many coastal fisheries are subject to harvesting externalities due to inadequate regulations compounded by limited enforcement. Coastal fisheries in Liberia consist of a fleet of dugout canoes (Kru) primarily targeting demersal finfish, larger open wooden boats propelled with outboard engines targeting small inshore pelagics (Fanti), and a small number of industrial trawlers employing midwater and bottom trawls targeting finfish and shrimp. This paper develops a bio-economic model for the coastal fisheries in Liberia and employs the model to identify economic optimal fishing effort and harvesting trajectories for the different coastal fleets. The results show under harvesting and disinvestments in the coastal fisheries in Liberia. In 2010 the Government of Liberia declared a six nautical mile inshore exclusion zone accessible only to small-scale fisheries (SSF), which was accompanied by increased enforcement. The coastal fleets in 2016 were profitable but the distribution of profits was tilted to the small-scale fleets. The government needs to evaluate what policy options are available to fully utilize the fisheries potential for different species complexes while at the same time reduce the risk of conflict and overharvesting. There appears to be a need for investment in new technologies, which can only take place if fishing in Liberia will remain profitable.

Implications of interference among fishing vessels and the ideal free distribution to the interpretation of CPUE

1998 ◽  
Vol 55 (1) ◽  
pp. 37-46 ◽  
Author(s):  
D M Gillis ◽  
R M Peterman
Keyword(s):  
Ideal Free Distribution ◽  
Fishing Effort ◽  
Catch Per Unit Effort ◽  
Free Distribution ◽  
Fishing Vessels ◽  
Factor Interactions ◽  
The Relationship ◽  
Index Of Abundance ◽  
Ideal Free ◽  
The Ideal

Despite recognized biases, catch per unit effort (CPUE) statistics remain widely used for the estimation of fish abundance. Previous workers have shown that CPUE can be a misleading index of abundance due to fish behavior, the nominal effort units used, and increases through time in efficiency of fishing (catchability). We examine the theoretical implications of a different factor, interactions among fishing vessels, for the relationship between abundance and CPUE. Our model simulates a fishery that occurs in several adjacent fishing grounds. The spatial distribution of catch and effort is based on a simplification of the Baranov catch equation, the relationship between fishing efficiency and local fishing effort (interference), and the assumptions of the ideal free distribution. Our results indicate that (i) even low levels of interference among fishing vessels can cause a breakdown in the correlation between CPUE and local abundance and (ii) the influence of interference on this relationship is dependent on the correlation of abundances among adjacent areas. Our model suggests an alternative index of abundance, based on the proportion of fishing effort on a ground, that would be appropriate for cases where interference occurs among fishing gear.

scholarly journals Combining participatory and socioeconomic approaches to map fishing effort in small-scale fisheries

PLoS ONE ◽  
2017 ◽  
Vol 12 (5) ◽  
pp. e0176862 ◽  
Author(s):  
Lauric Thiault ◽  
Antoine Collin ◽  
Frédérique Chlous ◽  
Stefan Gelcich ◽  
Joachim Claudet
Keyword(s):  
Fishing Effort ◽  
Small Scale ◽  
Small Scale Fisheries

Hierarchical interpretation of nonlinear relationships linking yellowfin tuna (Thunnus albacares) distribution to the environment in the Atlantic Ocean

2001 ◽  
Vol 58 (3) ◽  
pp. 458-469 ◽  
Author(s):  
Olivier Maury ◽  
Didier Gascuel ◽  
Francis Marsac ◽  
Alain Fonteneau ◽  
Anne-Laure De Rosa
Keyword(s):  
Adult Population ◽  
Yellowfin Tuna ◽  
Additive Models ◽  
Small Scale ◽  
Physical Factors ◽  
Thunnus Albacares ◽  
Catch Per Unit Effort ◽  
Low Salinity ◽  
Nonlinear Relationships ◽  
Unit Effort

Using generalized additive models, we show evidence for nonlinear relationships between various hydrological factors and age-structured catch per unit effort of Atlantic yellowfin tuna (Thunnus albacares) for two fishing fleets. Catchability effects are distinguished from tuna environmental preference effects in the catch per unit effort variability. With respect to catchability, an important nonlinear effect of local fishing effort is highlighted for each fleet. It is interpreted as resulting from a local overfishing phenomenon of adult yellowfin tuna and from vessel fishing tactics (cooperation/spying). The environmental preferences obtained facilitate the interpretation of the hierarchical spatial distribution and age-dependent movements of the yellowfin population. We show that, on a large spatiotemporal scale (the whole ocean), low salinity is a good predictor of yellowfin habitat. Juveniles are mainly distributed in low-salinity waters (<0.035 kg·kg–1) when adults extend their range to waters of 0.036 kg·kg–1. On a mesoscale, adult population annual reproductive transatlantic displacements are probably driven by temperature and salinity gradients to warm and low-salinity locations that are favorable for juveniles. North–south seasonal movements of the population are clearly related to warmwater seasonal oscillations. On a small scale, ocean thermic stability and gradients of sea surface temperature are important physical factors determining yellowfin concentration.

Movement Dynamics in a Fishery: Application of the Ideal Free Distribution to Spatial Allocation of Effort

1993 ◽  
Vol 50 (2) ◽  
pp. 323-333 ◽  
Author(s):  
Darren M. Gillis ◽  
Randall M. Peterman ◽  
Albert V. Tyler
Keyword(s):  
Spatial Distribution ◽  
Ideal Free Distribution ◽  
Fishing Effort ◽  
Catch Per Unit Effort ◽  
Exploitation Competition ◽  
Spatial Allocation ◽  
Free Distribution ◽  
Fishing Vessels ◽  
Ideal Free ◽  
The Ideal

Many traditional analyses of fisheries data assume that there is a negligible effect of alternative fish stocks on the spatial distribution of fishing effort and that the amount of local effort does not influence catchability. There is growing evidence that contradicts these assumptions. Because of the potential biases that these erroneous assumptions may cause in the interpretation of catch-per-unit-effort (CPUE) statistics, it is important to determine the factors governing the spatial distribution of effort in a fishery. We used data on the Hecate Strait, British Columbia, Canada, trawl fishery to test hypotheses about spatial allocation of effort and interaction among fishing vessels. The ideal free distribution of Fretwell and Lucas (1970. Acta Biotheor. 19: 16–36) was the foundation for deriving these tests. We found evidence for competition among vessels, although we could not distinguish whether the mechanism was interference or exploitation competition. As well, CPUE was generally equalized among the areas fished, as predicted by the ideal free distribution, because of movement of boats among areas. Thus, area-specific CPUE would not be a reliable index of relative abundance of fish in different areas; relative fishing effort may be better.

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