Peraltilla S.,IMARPE |
Bertrand S.,CRH Inc
Fisheries Research | Year: 2014
While speed of fish schools is critical information for parameterizing numerous ecosystem models and evaluating fishery management options, it is poorly documented. Here we present results of in situ measurements of the speed of Peruvian anchovy schools, a small pelagic species that sustain the world's largest mono-specific fishery. Instantaneous school speed was in average 0.6ms-1, authorizing theoretical maximum displacements of ~26kmday-1. © 2013 Elsevier B.V.
Joo R.,IMARPE |
Joo R.,CIRAD - Agricultural Research for Development |
Salcedo O.,University of Lima |
Gutierrez M.,University of Lima |
And 2 more authors.
Fisheries Research | Year: 2015
Understanding the spatiotemporal behavior of fishermen at the fleet scale is key for defining effective strategies for fisheries management. Here we classify the spatial patterns exhibited by fishing trip trajectories in the world's largest monospecific fishery, the Peruvian anchovy fishery. Our goal is to identify spatial strategies and their possible changes over 2000-2009. The data comprise more than 350,000 fishing trips, recorded using a vessel monitoring system. On-board observers monitored a small fraction of those trips (>2000), providing data for inferring the type of activity (fishing, searching, and cruising) from the position records, for use in a state-space model. Each fishing trip was characterized by its duration, maximum distance to the coast, geographical extension, and time spent fishing, searching and cruising. Using clustering techniques, we identified four types of fishing trips, associated with differences in management among regions, fleet segments, and skippers' behavior. The methodology could be used to investigate fishing spatial strategies using VMS trajectories in other fisheries. © 2014 Elsevier B.V.
Freon P.,IRD Montpellier |
Sueiro J.C.,Cayetano Heredia Peruvian University |
Iriarte F.,IandA |
Miro Evar O.F.,University Tumbes |
And 3 more authors.
Reviews in Fish Biology and Fisheries | Year: 2014
Peru is the top exporter of fishmeal and fish oil (FMFO) worldwide and is responsible for half and a third of global production, respectively. Landings of "anchoveta" (Engraulis ringens) are used nearly exclusively for FMFO production, despite a proactive national food policy aimed at favoring the direct human consumption of this inexpensive species. It may be surprising that in a country where malnutrition and caloric deficit constitute major issues, a low-priced and highly nutritious fish such as anchovy does not have stronger domestic demand as a food fish. Here, we review and assess eight potential politico-socio-economic processes that can explain this situation. The main explanation are dietary habits, the preference for broiler and the higher profit from anchovy sold as feed fish compared to its use as a food fish due to historically high FMFO prices, boosted by an increasing demand for aquaculture in a context of finite forage and trash fish resources. In addition, the recent introduction of an individual quota system has shifted bargaining power from processors to fishers, thereby increasing competition for the raw material. This competition results in an increase in anchovy prices offered by the feed fish industry due to its onshore processing overcapacity, which is detrimental to the food fish industry. In the end, although the dominant use of anchovy for fish feed is largely explained by integrating these market mechanisms and other minor ones, this use raises other issues, such as rent redistribution through public policies, employment, equitability and utility (low social costs), and resource management (threats to ecosystems or global change). Different policy scenarios are proposed in relation to these issues. © 2013 Springer Science+Business Media Dordrecht.
Lorrain A.,French National Center for Scientific Research |
Arguelles J.,IMARPE |
Alegre A.,IMARPE |
Bertrand A.,IMARPE |
And 3 more authors.
PLoS ONE | Year: 2011
Background: Cephalopods play a major role in marine ecosystems, but knowledge of their feeding ecology is limited. In particular, intra- and inter-individual variations in their use of resources has not been adequatly explored, although there is growing evidence that individual organisms can vary considerably in the way they use their habitats and resources. Methodology/Principal Findings: Using δ 13C and δ 15N values of serially sampled gladius (an archival tissue), we examined high resolution variations in the trophic niche of five large (>60 cm mantle length) jumbo squids (Dosidicus gigas) that were collected off the coast of Peru. We report the first evidence of large inter-individual differences in jumbo squid foraging strategies with no systematic increase of trophic level with size. Overall, gladius δ 13C values indicated one or several migrations through the squid's lifetime (~8-9 months), during which δ 15N values also fluctuated (range: 1 to 5‰). One individual showed an unexpected terminal 4.6‰ δ 15N decrease (more than one trophic level), thus indicating a shift from higher- to lower-trophic level prey at that time. The data illustrate the high diversity of prey types and foraging histories of this species at the individual level. Conclusions/Significance: The isotopic signature of gladii proved to be a powerful tool to depict high resolution and ontogenic variations in individual foraging strategies of squids, thus complementing traditional information offered by stomach content analysis and stable isotopes on metabolically active tissues. The observed differences in life history strategies highlight the high degree of plasticity of the jumbo squid and its high potential to adapt to environmental changes. © 2011 Lorrain et al.
Joo R.,CIRAD - Agricultural Research for Development |
Bertrand S.,CIRAD - Agricultural Research for Development |
Chaigneau A.,IMARPE |
Chaigneau A.,University Pierre and Marie Curie |
Ecological Modelling | Year: 2011
The spatial behavior of numerous fishing fleets is nowadays well documented thanks to satellite Vessel Monitoring Systems (VMS). Vessel positions are recorded on a frequent and regular basis which opens promising perspectives for improving fishing effort estimation and management. However, no specific information is provided on whether the vessel is fishing or not. To answer that question, existing works on VMS data usually apply simple criteria (e.g. threshold on speed). Those simple criteria generally focus in detecting true positives (a true fishing set detected as a fishing set); conversely, estimation errors are given no attention. For our case study, the Peruvian anchovy fishery, those criteria overestimate the total number of fishing sets by 182%. To overcome this problem an artificial neural network (ANN) approach is presented here. In order to set both the optimal parameterization and use " rules" for this ANN, we perform an extensive sensitivity analysis on the optimization of (1) the internal structure and training algorithm of the ANN and (2) the " rules" used for choosing both the relative size and the composition of the databases (DBs) used for training and inferring with the ANN. The " optimized" ANN greatly improves the estimates of the number and location of fishing events. For our case study, ANN reduces the total estimation error on the number of fishing sets to 1% (in average) and obtains 76% of true positives. This spatially explicit information on effort, provided with error estimation, should greatly reduce misleading interpretations of catch per unit effort and thus significantly improve the adaptive management of fisheries. While fitted on Peruvian anchovy fishery data, this type of neural network approach has wider potential and could be implemented in any fishery relying on both VMS and at-sea observer data. In order to increase the accuracy of the ANN results, we also suggest some criteria for improving sampling design by at-sea observers and VMS data. © 2010 Elsevier B.V.