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Fisheries Managers (fisheries + managers)
Selected AbstractsORIGINAL ARTICLE: Implications of fisheries-induced evolution for stock rebuilding and recoveryEVOLUTIONARY APPLICATIONS (ELECTRONIC), Issue 3 2009Katja Enberg Abstract Worldwide depletion of fish stocks has led fisheries managers to become increasingly concerned about rebuilding and recovery planning. To succeed, factors affecting recovery dynamics need to be understood, including the role of fisheries-induced evolution. Here we investigate a stock's response to fishing followed by a harvest moratorium by analyzing an individual-based evolutionary model parameterized for Atlantic cod Gadus morhua from its northern range, representative of long-lived, late-maturing species. The model allows evolution of life-history processes including maturation, reproduction, and growth. It also incorporates environmental variability, phenotypic plasticity, and density-dependent feedbacks. Fisheries-induced evolution affects recovery in several ways. The first decades of recovery were dominated by demographic and density-dependent processes. Biomass rebuilding was only lightly influenced by fisheries-induced evolution, whereas other stock characteristics such as maturation age, spawning stock biomass, and recruitment were substantially affected, recovering to new demographic equilibria below their preharvest levels. This is because genetic traits took thousands of years to evolve back to preharvest levels, indicating that natural selection driving recovery of these traits is weaker than fisheries-induced selection was. Our results strengthen the case for proactive management of fisheries-induced evolution, as the restoration of genetic traits altered by fishing is slow and may even be impractical. [source] Real options for precautionary fisheries managementFISH AND FISHERIES, Issue 2 2008Eli P Fenichel Abstract The 1996 Food and Agriculture Organization's (FAO) ,Guidelines on the Precautionary Approach to Fisheries and Species Introduction' raise important issues for fisheries managers, but fail to prescribe an approach for risk management. The distinguishing characteristics of the ,precautionary approach' are the inclusion of uncertainty and ,an elaboration on the burden of proof'. The FAO precautionary approach emphasizes that managers should be risk-averse, but does not provide tools for determining the appropriate degree of risk aversion. Consequently, application of the precautionary approach often leads to decision-making based on ad hoc safety margins. These safety margins are seldom chosen with explicit consideration of trade-offs. If the emphasis was shifted to choosing between competing uncertainties, then managers could manage risk. By attempting to avoid risk, managers may gain exposure to other risks and perhaps miss valuable opportunities. We place fishery management problems within the rubric of ,real investment' problems, and compare and contrast the consideration of risk by alternative investment frameworks. We show that traditional investment frameworks are inappropriate for fishery management, and furthermore, that traditional precautionary approaches are arbitrary and without basis in decision theory. Quantitative decision-making techniques, such as formal decision analysis (FDA), enable integration of competing hypotheses that help alleviate burden-of-proof issues. These techniques help analysts consider sources of uncertainty. FDA, however, can still be subject to arbitrary safety margins because such analyses often focus on determining which strategies best achieve, or avoid, targets that have been established without complete consideration of trade-offs. A managerial finance approach, real options analysis (ROA), is an alternative and complementary decision-making technique that enables managers to compute precautionary adjustments that couple the size of the ,safety margin' with the amount of uncertainty, thereby optimizing risk exposure and avoiding the need for arbitrary safety margins. We illustrate the advantages of an approach that combines FDA and ROA, using a heuristic example about a decision to re-introduce Atlantic salmon (Salmo salar L.) into Lake Ontario. Finally, we provide guidance on applying ROA to other fishery problems. The precautionary approach requires that managers consider risk, but considering risk is not the same as managing it. Here ROA is useful. [source] Seasonal variation in rod recapture rates indicates differential exploitation of Atlantic salmon, Salmo salar, stock componentsFISHERIES MANAGEMENT & ECOLOGY, Issue 3 2007J. L. THORLEY Abstract, Differential exploitation of the various components of a fish stock can adversely affect the diversity, abundance and long-term survival of the entire stock. Many anadromous salmonid stocks exhibit a seasonal structuring of their run-timing that allows fisheries managers to map monthly rod catches onto stock components. To estimate the rod exploitation levels of the various run-timing groups, fishing guides on the River Spey, Scotland, floy-tagged 786 rod-caught and released Atlantic salmon, Salmo salar L., between 2000 and 2002 and recorded recaptures. Whereas 25% of the fish tagged early in March were recaptured, only 2% of those tagged early in June were caught a second time. Exploitation is biased towards the early-running stock components which current assessments show to be least abundant. Management of Atlantic salmon based on an average exploitation rate is inappropriate. [source] Geolocation of Atlantic cod (Gadus morhua) movements in the Gulf of Maine using tidal informationFISHERIES OCEANOGRAPHY, Issue 4 2007J. P. GRÖGER Abstract Information derived from archival tags (digital storage tags, DSTs) were used to backtrack the migration of 11 tagged Atlantic cod (Gadus morhua) during 2001 in Massachusetts Bay, the Gulf of Maine, and Georges Bank. The DST tags continuously recorded time, temperature and depth. To geolocate fish positions during its time at large, we first extracted the tidal signal from the pressure recordings on the DST tags, and then compared the resulting data to data predicted with a Massachusetts Bay tidal model that provided us with geographical coordinates at a given date and time. Using least-squares criteria within an estimated geographical region of confidence that was constrained by biological and statistical information (e.g. swimming speed, known release and recapture location, and bottom depth) we were able to geolocate the fish. The resultant geolocated migration tracks indicate a large degree of movement of Atlantic cod in the region and an elevated importance of the Great South Channel (GSC) migration corridor between Massachusetts Bay and the western Georges Bank and Nantucket Shoals region. This observation contrasts strongly with inferences of limited movements by Atlantic cod based on conventional tag recapture methods (mean of 1200 km traveled versus 44 km traveled as measured by conventional tagging and geolocation, respectively). This study demonstrates that geolocation methodologies applied to archival tag studies hold great promise of becoming an important new tool for fisheries managers to quantify the movements of fishes. It also points out the need for greater collaboration between fisheries scientists and oceanographers, and particularly for the development of improved tidal models to cover stock regions more accurately and with higher precision. [source] Age, growth and sexual development of solenette, Buglossidium luteum (Risso, 1810), in the central Aegean SeaJOURNAL OF APPLIED ICHTHYOLOGY, Issue 3 2010A. T., lkyaz Summary Age, growth, spawning period and maturity of the solenette (Buglossidium luteum Risso, 1810) were studied in the central Aegean Sea to provide fisheries managers with essential data for science-based management. A total of 1220 samples were collected by trawl hauls from July 2004 to June 2007 in ,zmir Bay (Turkey). Sample sizes ranging from 5.3 to 11.6 cm total length were composed of 46% females, 32% males and 22% immature individuals, with a female to male ratio of 1 : 0.7. Age composition stages of the females were from I to IV, and males between I and III. The length,weight relationship was calculated as W = 0.0101L3.008 for all samples. Estimated von Bertalanffy growth parameters were L = 13.30 cm, to = ,0.440 year and k = 0.481 year,1, with a growth performance index of 1.93 (,'). The spawning period began in April and continued until July. Lengths at first maturity of females and males were 8.1 and 7.9 cm total length, respectively. Both sexes matured at the age of 2 years. [source] Anthropology and Fisheries Management in the United StatesANNALS OF ANTHROPOLOGICAL PRACTICE, Issue 1 2007Palma Ingles The collection of articles in this volume of NAPA Bulletin describes various types of social science research currently conducted in support of federal and state fisheries management by anthropologists and sociologists studying fishing-dependent communities and fisheries participants. The contributors work for NOAA, National Marine Fisheries Service (NMFS); various state fisheries agencies; in academia; or as contract researchers. These articles represent a wide geographical range, employ a diverse set of methods, and demonstrate different research goals ranging from responding to specific statutory or management requirements to establishing broader baseline social information to exploring the theoretical constructs that constrain or advance the field of applied anthropology in fisheries. This introduction provides background to the recent expansion of anthropological capacity in U.S. fisheries management and the divergent methods employed by practitioners. The range of methods includes classic ethnography and survey methods, cultural modeling, participatory research, and quantitative indicators-based assessment. The compilation of articles presents an opportunity to think about standardizing some methodological approaches for certain types of tasks, while expanding the array of accepted methodologies available to anthropologists advising fisheries managers. [source] A Marquesan coral reef (French Polynesia) in historical context: an integrated socio-ecological approachAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 6 2009Shankar Aswani Abstract 1.Marine biologists are increasingly aware of the impact that even small human populations can have on coral reefs around the world, while conservationists and fisheries managers have a growing appreciation of the importance of culturally informed management strategies in coral reef conservation efforts. Despite these recognitions, however, examples of integrated field studies are limited. 2.In this paper evidence from various disciplines is used to study the interaction between humans and one of the largest reefs in the Marquesas Islands, at Anaho Bay, Nuku Hiva Island, with the aim of assessing possible anthropogenic impacts over time. 3.First, it reports on a marine biological survey of the benthic substrates of the bay and the taxonomic composition and spatial distributions of the local fish species. Second, it draws on results from an ongoing archaeological study and integrates these with interviews of village elders to gain a historical perspective on the reef and potential human impacts. 4.The biological results indicated that the reef is in a state of decline, although fish densities are moderately high. The archaeological evidence, in turn, demonstrates that human populations have occupied this valley for at least the last 700 years. Throughout this period marine resources have been an important source of both food and raw materials for tools. The archaeological study also highlights aspects of landscape change, both natural and human-induced, that probably have been detrimental to reef health. 5.Using the combined biological and anthropological data, this paper considers the nexus of factors that have led to the current reef conditions and considers management issues for the future. Key in this regard are processes that have initiated erosion and soil run-off, and fluctuations in the local human populations. Copyright © 2008 John Wiley & Sons, Ltd. [source] | |||||||||||||