Comparing an ecosystem approach to single-species stock assessment: The case of Gazi Bay, Kenya

2018 ◽  
Vol 184 ◽  
pp. 1-14 ◽  
Author(s):  
Paul M. Tuda ◽  
Matthias Wolff
Keyword(s):  
Stock Assessment ◽  
Single Species ◽  
Ecosystem Approach ◽  
Gazi Bay

scholarly journals Dynamic of the Flemish Cap commercial stocks: use of a Gadget multispecies model to determine the relevance and synergies among predation, recruitment, and fishing

2017 ◽  
Vol 74 (4) ◽  
pp. 582-597 ◽  
Author(s):  
A. Pérez-Rodríguez ◽  
D. Howell ◽  
M. Casas ◽  
F. Saborido-Rey ◽  
A. Ávila-de Melo
Keyword(s):  
Species Interactions ◽  
Gadus Morhua ◽  
Stock Assessment ◽  
Single Species ◽  
Ecosystem Approach ◽  
Strong Interactions ◽  
Initial State ◽  
Northern Shrimp ◽  
Multispecies Model ◽  
Multispecies Modeling

Multispecies modeling is being increasingly accepted in stock assessment, especially in the context of an ecosystem approach to fisheries management (EAF). To achieve a future implementation of an EAF in the Flemish Cap, we present a multispecies model developed in Gadget, which covers the main commercial stocks over the period 1988–2012: cod (Gadus morhua), redfish (Sebastes spp.), and northern shrimp (Pandalus borealis). The model highlights the interdependent dynamic of these stocks and reveals strong interactions among recruitment, fishing, and predation (including cannibalism). These drivers have shown marked changes in their relative importance by species, age, and length over time, producing a transition from a traditional redfish- and cod-dominated system in the early 1990s to an intermediate shrimp and other fish species state by the late 1990s and in turn back to something close to the initial state by the late 2000s. The multispecies model developed in this paper shows that disregarding the species interactions would lead to serious underestimates of natural mortality and overestimations of the exploitable biomass and highlights the need to move beyond single-species management in this highly coupled ecosystem.

The sea pens Virgularia mirabilis, Pennatula phosphorea and Funiculina quadrangularis: distribution and conservation issues in Scottish waters

2007 ◽  
Vol 87 (5) ◽  
pp. 1095-1103 ◽  
Author(s):  
Clare F. Greathead ◽  
David W. Donnan ◽  
James M. Mair ◽  
Graham R. Saunders
Keyword(s):  
Stock Assessment ◽  
Action Plan ◽  
Ecosystem Approach ◽  
Geographical Information ◽  
Video Footage ◽  
Commercial Species ◽  
The Uk ◽  
Video Surveys ◽  
Marine Laboratory ◽  
Future Management

The distributions of the pennatulid anthozoans (sea pens) Virgularia mirabilis, Pennatula phosphorea and Funiculina quadrangularis in Scottish waters have previously only been extensively documented in sea lochs, by the Marine Nature Conservation Review (MNCR) surveys. Funiculina quadrangularis in particular was thought to be restricted to the deep basins of sea lochs and is classified as a nationally uncommon species. Sea pens are characterizing species in seven biotopes found in Scottish waters and are protected under the ‘Mud in Deep Water Habitat Action Plan’ of the UK Biodiversity Action Plan (UKBAP) and are also recorded in several Special Areas of Conservation. The present study has extended the existing information available on sea pens in Scottish waters. The distribution and abundance of the three sea pen species were mapped using GIS (Geographical Information System) by utilizing data from Nephrops norvegicus stock assessment video surveys carried out by Fisheries Research Services (FRS) Marine Laboratory. Distribution was shown to be aggregated for all species. Funiculina quadrangularis was present in areas outside the sea lochs, such as the South Minch and the outer mouths of most sea lochs. This study demonstrates that analysis of video footage derived from Nephrops stock assessment surveys can significantly extend our knowledge of sea pen distribution and population density. Future management of Nephrops stocks can be expected to consider impacts of fishing on non-commercial species such as sea pens as a part of the ‘ecosystem approach’ to management.

Incorporating habitat preference into the stock assessment and management of blue marlin (Makaira nigricans) in the Pacific Ocean

2012 ◽  
Vol 63 (7) ◽  
pp. 565 ◽  
Author(s):  
Nan-Jay Su ◽  
Chi-Lu Sun ◽  
André E. Punt ◽  
Su-Zan Yeh ◽  
Gerard DiNardo
Keyword(s):  
Population Dynamics ◽  
Habitat Preference ◽  
Stock Assessment ◽  
Ecosystem Approach ◽  
Maximum Sustainable Yield ◽  
Blue Marlin ◽  
Makaira Nigricans ◽  
Biological Variables ◽  
Population Dynamics Model ◽  
Spawning Stock

Stock assessments that include a spatial component or relate population dynamics to environmental conditions can be considered one way of implementing an ecosystem approach to fisheries. A spatially-structured population dynamics model that takes account of habitat preference is developed and then applied to Pacific blue marlin (Makaira nigricans), as they prefer certain habitats and migrate seasonally. The model is fitted to fishery catch-rate and size data, along with information on the relative density of the population over space derived from a habitat preference model fitted to oceanographic and biological variables. Results show that blue marlin are more abundant in tropical waters, and females account for most of the biomass. Assessments that allow for environmental factors, movement dynamics and sexual dimorphism indicate that this population is in an over-exploited state, with current spawning stock biomass below the level corresponding to maximum sustainable yield (SMSY) and current fishing mortality exceeding that needed to achieve MSY (FMSY). A risk analysis based on samples from a Bayesian posterior distribution suggests that the population will remain above SMSY after 20 years if exploitation rates are below the level corresponding to FMSY.

scholarly journals Advancing ecosystem management strategies for the Gulf of Mexico's fisheries resources: implications for the development of a fishery ecosystem plan

2020 ◽  
Vol 96 (4) ◽  
pp. 617-640
Author(s):  
Andrea Dell'Apa ◽  
Joshua P Kilborn ◽  
William J Harford
Keyword(s):  
Fisheries Management ◽  
Ecosystem Management ◽  
Fishery Management ◽  
Planning Process ◽  
Marine Ecosystem ◽  
Management Strategies ◽  
Single Species ◽  
Ecosystem Approach ◽  
Large Marine Ecosystems ◽  
The Us

Recent global improvements to fisheries sustainability have been made through the adoption of more holistic management frameworks, such as the ecosystem approach to fisheries management (EAFM) and ecosystem-based fisheries management (EBFM), and a concurrent transition from a focus on single species or stocks to multispecies and ecosystems. In the US, federal and regional fisheries management encompass multiple layers of comprehensive, ecosystem focused management strategies for living marine resources within its network of large marine ecosystems (LMEs). Here, we provide an overview for the US portion of the Gulf of Mexico large marine ecosystem (GOM-LME) by examining multiple aspects of its fishery management scheme through the lenses of EAFM, EBFM, and the integrated ecosystem assessment (IEA) framework that has been used worldwide to advise, inform, and operationalize ecosystem management. The US-GOM's fishery management and ecosystem community appears to be keeping pace with other US regional efforts. However, more tools like fishery ecosystem plans (FEPs), which are conducive to the effective integration of ecosystem considerations into fishery management processes, are needed to inform and guide the work of regional managers, decision-makers, and stakeholders. Therefore, we propose a structured planning process aimed at advancing the development and implementation of a GOM-FEP, and describe two case studies of EAFM and EBFM applications, respectively, that can help to navigate through our proposed planning process. This work offers strategic guidance and insights to support efforts of regional fishery managers to translate ecosystem management principles, approaches, and objectives into an "action oriented" FEP in the GOM-LME.

scholarly journals HABITAT USE STRATEGY OF VERTEBRATES IN AN EMERGING NATURE RESERVE

2019 ◽  
Vol 17 (2) ◽  
pp. 50-80
Author(s):  
A. L.A. SHOTUYO ◽  
O. A. JAYEOLA ◽  
I. A. AYODELE
Keyword(s):  
Habitat Use ◽  
Animal Species ◽  
Nature Reserve ◽  
Stock Assessment ◽  
Strong Association ◽  
Principal Component ◽  
Single Species ◽  
Line Transect ◽  
The Family ◽  
And Control

The habitat use strategy of vertebrates in Alabata Strict Nature Reserve was studied. Twenty (20) sample plots of 25m x 25m (0.062ha) were laid at random over the total area of the study site for data collection. King Census and Line Transect methods were modified for this study using direct and indirect modes of wildlife stock assessment for an accurate collection of data due to the dense nature of the vegetation in some areas. One hundred and twenty-one vertebrate species, belonging to fifty-six families were recorded. Twenty-seven families were represented by just a single species each, while thirteen families had two species each. The family Colubridae was represented by ten species, while Rattudae and  Sciuridae had a single species respectively. Birds were the most encountered (more than 60%) followed by mammals (more than 20%) while the Order Reptalia constitutes the remaining (less than 20%). Food and cover requirements abound in the study area, which explains the availability of a variety of fauna species. There is a strong association between the environmental variables and animal species thus; distribution, performance and survival of the species are directly influenced by these variables. The Principal component analysis and Ordination shows that the ecosystem of the study site is not stable yet. This can be observed from the clustering of the animal species together in an attempt to make the best use of the environment. The maintenance of a healthy ecosystem is largely dependent on its management and control of activities of man and animals.  

Enhancing single-species stock assessments with diverse ecosystem perspectives: a case study for Gulf of Mexico Red Grouper (Epinephelus morio) and red tides

2021 ◽  
Author(s):  
Skyler R Sagarese ◽  
Nathan R. Vaughan ◽  
John F Walter III ◽  
Mandy Karnauskas
Keyword(s):  
Gulf Of Mexico ◽  
Stock Assessment ◽  
Red Tide ◽  
Single Species ◽  
Unintended Consequences ◽  
Red Tides ◽  
Considerable Uncertainty ◽  
Red Grouper ◽  
Near Term ◽  
Stock Depletion

Impacts of Karenia brevis red tide blooms have been an increasing cause of concern for fisheries management in the Gulf of Mexico (Gulf). The 2019 Gulf red grouper stock assessment was confronted with the challenges of quantifying and parameterizing red tides during both historical and projection time-periods. Red tide mortality was estimated for each age-class in the model solely in 2005 and 2014 during severe events. Given the considerable uncertainty surrounding the 2018 red tide and its substantial implications on the status of the population, several projection scenarios were evaluated. Under the assumption of no 2018 red tide mortality, near-term catches were projected to nearly double, a predicted outcome that appeared to be in contrast to recent record low catches and fishing industry perceptions of significant stock depletion. In the event that the 2018 red tide caused mortality, but was not accounted for in projections, the recommended catch levels would lead to high probabilities of overfishing and potentially stock collapse. Collectively, these results highlight how consideration of uncertainty in projections can help avoid unintended consequences.

scholarly journals An investigation into fisheries interaction effects using Atlantis

2014 ◽  
Vol 72 (1) ◽  
pp. 275-283 ◽  
Author(s):  
Michael D. Smith ◽  
Elizabeth A. Fulton ◽  
Robert W. Day
Keyword(s):  
Fisheries Management ◽  
Carrying Capacity ◽  
Stock Assessment ◽  
Single Species ◽  
Interaction Effects ◽  
Fishing Effort ◽  
Maximum Sustainable Yield ◽  
Simultaneous Increase ◽  
Total Catch ◽  
The Impact

Abstract Fisheries management is commonly based on the outputs of single-species stock assessment models. While such models are appropriate for tactical issues such as quota setting, they typically omit explicit trophic interactions between different parts of the ecosystem. To successfully manage multiple fisheries in the same ecosystem, we need to understand how fishing one species may indirectly affect other species. In this paper, we used a simulation model of the southern Benguela ecosystem, built in the Atlantis framework, to explore fisheries interaction effects. We first measured the impact of fishing different stocks individually at FMSY, the hypothetical level of fishing effort which produces maximum sustainable yield (MSY) in a single-species modelling context. We then applied FMSY to all stocks simultaneously and compared the simultaneous yield with the sum of yields from the individual applications of FMSY. Contrary to expectations, the total catch was higher under the simultaneous scenario. We explored our results by studying the influences of trophic interaction between species at different levels of the foodweb, and found that our overall result was driven by two key factors: volumetric dominance of small pelagic fish in the total catch, and asymmetric influences of competition and predation between piscivorous and planktivorous species. The simultaneous increase in fishing pressure across multiple species in the model led to increased effective carrying capacity for small pelagic species (due to reduced competition), but reduced carrying capacity for piscivorous species (due to reduced small pelagic prey). This work has important implications for the design of tactical multispecies models for use in ecosystem-based fisheries management.

scholarly journals Modeling energy flow in a large Neotropical reservoir: a tool do evaluate fishing and stability

2006 ◽  
Vol 4 (2) ◽  
pp. 253-260 ◽  
Author(s):  
Ronaldo Angelini ◽  
Angelo Antonio Agostinho ◽  
Luiz Carlos Gomes
Keyword(s):  
Steady State ◽  
Energy Flow ◽  
Stock Assessment ◽  
Ecosystem Approach ◽  
Fishing Effort ◽  
Ecopath With Ecosim ◽  
Tropical Ecosystems ◽  
Energy Flows ◽  
Over Time

Recently, there is an increasing perception that the ecosystem approach gives important insights to support fisheries stock assessment and management. This paper aims to quantify energy flows in the Itaipu Reservoir (Brazil) and to simulate increase of the fishing effort of some species, using Ecopath with Ecosim software, which could allow inferences on stability. Therefore, two steady-state Itaipu models were built (1983-87 and 1988-92). Results showed that: a) there are no differences between models, and results on aging trends do not vary over time indicating that fishery does not alter the ecosystem as a whole; b) results of fisheries simulations are approximate to mono-specific stock assessment for the same species and periods; c) many authors believe that tropical ecosystems are environments where biotic and abiotic oscillations are annual and sometimes unexpected, but the results found for the Itaipu Reservoir indicate that stability was met after 16 years.

scholarly journals Failure to eliminate overfishing and attain optimum yield in the New England groundfish fishery

2013 ◽  
Vol 71 (2) ◽  
pp. 226-233 ◽  
Author(s):  
Brian J. Rothschild ◽  
Emily F. Keiley ◽  
Yue Jiao
Keyword(s):  
New England ◽  
Management System ◽  
Fishery Management ◽  
Stock Assessment ◽  
Single Species ◽  
Recent Change ◽  
Production Model ◽  
Optimum Yield ◽  
Management Regime ◽  
Groundfish Fishery

Abstract Rothschild, B. J., Keiley, E. F., and Jiao, Y. 2014. Failure to eliminate overfishing and attain optimum yield in the New England groundfish fishery. – ICES Journal of Marine Science, 71: 226–233. Under US law, fishery management is required to eliminate overfishing and attain optimum yield (OY). In New England, many groundfish stocks continue to be overfished, and the fishery continues to harvest less than OY. The reasons for the shortfalls are rooted in the socio-economic structure of the management regime, and technical and scientific issues that constrain the management system. The most recent change in the management regime (days-at-sea to catch shares) and performance relative to OY and the prevention of overfishing are analyzed along with metrics used to gauge performance. The commonly used age-based production model gives a problematic perception of stock abundance. Structural issues that seem to impair achieving OY are the adherence to the single-species interpretation of multiple-species yield and the use of the Fx% proxy. Simpler approaches to stock assessment are discussed. A management system that creates feasible goals and uses improved and simpler metrics to measure performance is needed to facilitate attainment of management goals.

Using food web model results to inform stock assessment estimates of mortality and production for ecosystem-based fisheries management

2010 ◽  
Vol 67 (9) ◽  
pp. 1490-1506 ◽  
Author(s):  
Sarah K. Gaichas ◽  
Kerim Y. Aydin ◽  
Robert C. Francis
Keyword(s):  
Food Web ◽  
Fisheries Management ◽  
Prey Availability ◽  
Stock Assessment ◽  
Marine Ecosystem ◽  
Single Species ◽  
Balance Model ◽  
Fishing Mortality ◽  
Important Species ◽  
Predation Mortality

Examining food web relationships for commercially important species enhances fisheries management by identifying sources of variability in mortality and production that are not included in standard single-species stock assessments. We use a static mass-balance model to evaluate relationships between species in a large marine ecosystem, the coastal Gulf of Alaska, USA. We focus on food web relationships for four case-study species: Pacific halibut ( Hippoglossus stenolepis ), longnose skate ( Raja rhina ), walleye pollock ( Theragra chalcogramma ), and squids (order Teuthoidea). For each, we present the species’ position within the food web, evaluate fishing mortality relative to predation mortality, and evaluate diet compositions. We find that high trophic level (TL) species, whether commercially valuable (halibut) or incidentally caught (skates), have mortality patterns consistent with single-species assessment assumptions, where fishing mortality dominates natural mortality. However, assessments for commercially valuable (pollock) or incidentally caught (squids) mid-TL species can be enhanced by including food web derived predation information because fishing mortality is small compared with high and variable predation mortality. Finally, we outline food web relationships that suggest how production of species may change with diet composition or prey availability.

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