Evaluating the sensitivity of ecological indicators with a perspective of temporal scales

2017 ◽  
Vol 68 (9) ◽  
pp. 1664
Author(s):  
Chongliang Zhang ◽  
Yong Chen ◽  
Yiping Ren ◽  
Rong Wan
Keyword(s):  
Trophic Interactions ◽  
Fishery Management ◽  
Community Dynamics ◽  
Ecological Indicators ◽  
Fishing Effort ◽  
Early Years ◽  
Size Spectrum ◽  
Fishing Pressure ◽  
Temporal Scales ◽  
Non Linear

This simulation study tests the sensitivity of 12 candidate ecological indicators (EIs) that characterise fish abundance, body size and trophodynamics with respect to temporal scales. Size-spectrum models that explicitly account for trophic interactions are used to simulate community dynamics under different levels of fishing pressure, including a specific model of the fish community in Haizhou Bay, China, and trait-based models of generalised fishery systems. The sensitivity of EIs is characterised by (1) responsiveness, which refers to the dynamics of EI values with respect to the magnitude of changes in fishing effort, and (2) detectability, which measures the relative changes of EI with respect to reference baselines. The response of EIs is substantially non-linear over time. Most EIs are responsive to the reduction of fishing effort and have low detectability under high fishing pressure. Both characteristics of sensitivity tend to increase in the early years and level off in 2 decades, suggesting transient behaviours in EI dynamics. The results suggested the essential non-linear dynamics of EIs resulting from underlying trophic interactions and the potential misinterpretation of the temporal EIs dynamics. We highlight the necessity of considering temporal scales and fishing characteristics in applying EIs in fishery management.

scholarly journals Responses of ecological indicators to fishing pressure under environmental change: exploring non-linearity and thresholds

2019 ◽  
Vol 77 (4) ◽  
pp. 1516-1531 ◽  
Author(s):  
Caihong Fu ◽  
Yi Xu ◽  
Arnaud Grüss ◽  
Alida Bundy ◽  
Lynne Shannon ◽  
...  
Keyword(s):  
Environmental Change ◽  
Primary Productivity ◽  
Ecological Indicators ◽  
Marine Ecosystems ◽  
Additive Models ◽  
Productivity Change ◽  
Fishing Pressure ◽  
Fishing Mortality ◽  
Fishing Strategies ◽  
Non Linear

Abstract Marine ecosystems are influenced by multiple stressors in both linear and non-linear ways. Using generalized additive models (GAMs) fitted to outputs from a multi-ecosystem, multi-model simulation experiment, we investigated 14 major ecological indicators across ten marine ecosystems about their responses to fishing pressure under: (i) three different fishing strategies (focusing on low-, high-, or all-trophic-level taxa); and (ii) four different scenarios of directional or random primary productivity change, a proxy for environmental change. From this work, we draw four major conclusions: (i) responses of indicators to fishing mortality in shapes, directions, and thresholds depend on the fishing strategies considered; (ii) most of the indicators demonstrate decreasing trends with increasing fishing mortality, with a few exceptions depending on the type of fishing strategy; (iii) most of the indicators respond to fishing mortality in a linear way, particularly for community and biomass-based indicators; and (iv) occurrence of threshold for non-linear-mixed type (i.e. non-linear with inflection points) is not prevalent within the fishing mortality rates explored. The conclusions drawn from the present study provide a knowledge base in indicators’ dynamics under different fishing and primary productivity levels, thereby facilitating the application of ecosystem-based fisheries management worldwide.

scholarly journals Sustainable exploitation of temperate fish stocks

2009 ◽  
Vol 6 (1) ◽  
pp. 124-127 ◽  
Author(s):  
Henrik Sparholt ◽  
Robin M. Cook
Keyword(s):  
Species Interactions ◽  
Fishery Management ◽  
Regional Scale ◽  
Single Species ◽  
Fishing Effort ◽  
Theoretical Concept ◽  
Maximum Sustainable Yield ◽  
Production Model ◽  
The Status ◽  
Long Time

The theory of maximum sustainable yield (MSY) underpins many fishery management regimes and is applied principally as a single species concept. Using a simple dynamic biomass production model we show that MSY can be identified from a long time series of multi-stock data at a regional scale in the presence of species interactions and environmental change. It suggests that MSY is robust and calculable in a multispecies environment, offering a realistic reference point for fishery management. Furthermore, the demonstration of the existence of MSY shows that it is more than a purely theoretical concept. There has been an improvement in the status of stocks in the Northeast Atlantic, but our analysis suggests further reductions in fishing effort would improve long-term yields.

scholarly journals Catch-per-unit-effort and size spectra of lake fish assemblages reflect underlying patterns in ecological conditions and anthropogenic activities across regional and local scales

2016 ◽  
Vol 73 (4) ◽  
pp. 535-546 ◽  
Author(s):  
Cindy Chu ◽  
Nigel P. Lester ◽  
Henrique C. Giacomini ◽  
Brian J. Shuter ◽  
Donald A. Jackson
Keyword(s):  
Body Size ◽  
Fish Assemblages ◽  
Anthropogenic Activities ◽  
Ecological Indicators ◽  
Size Spectrum ◽  
Catch Per Unit Effort ◽  
Ecological Processes ◽  
Boosted Regression Tree ◽  
Unit Effort ◽  
Lake Fish

Across broad geographic scales, ecological indicators for fish assemblages should represent causal ecological processes, be sensitive enough to show patterns across the landscape, and reflect underlying biotic or abiotic conditions that influence those patterns. We assessed the responses of commonly applied ecological indicators for lake fish assemblages (mean body size, catch-per-unit-effort (CPUE), and normalized length size spectrum (NLSS) slope) to regional (climate, water chemistry, and watershed stress due to human activities) and local (lake morphometry, water quality, and angling pressure) ecological and anthropogenic variables. The indicators were estimated using fish assemblage catch data acquired via a standardized gillnetting protocol implemented within 693 lakes in Ontario, Canada. To our knowledge, our study is the first size-based or catch-based indicator evaluation to include detailed observations of angling pressure on hundreds of inland lakes. Boosted regression tree models showed that CPUE of large-bodied organisms and NLSS slope best described underlying patterns in the regional and local variables. Models developed with a mix of regional and local variables performed better than models developed with regional or local variables alone. The relative influences of the variables and responses varied among indicators, but in general, ecological variables had greater influence on the indicators than anthropogenic variables. These results emphasize the complex and multiscaled nature of factors and ecological processes affecting body size, habitat-community production, and trophic dynamics in lake fish assemblages.

scholarly journals Overlooked biological and economic implications of within-season fishery dynamics

2014 ◽  
Vol 71 (2) ◽  
pp. 181-188 ◽  
Author(s):  
Xiaozi Liu ◽  
Mikko Heino
Keyword(s):  
Concentration Profile ◽  
Fishing Effort ◽  
Economic Consequences ◽  
Fish Abundance ◽  
Fishing Pressure ◽  
Fishing Mortality ◽  
Economic Implications ◽  
Special Cases ◽  
Total Stock ◽  
Stock Abundance

Catch equations relate fisheries catch to initial fish abundance and the applied fishing pressure. The Baranov catch equation, often simply referred to as the catch equation, is the commonest one. However, there are exactly three ways of describing seasonal progression of fishing parsimoniously with a single parameter: assume catch rate, fishing effort, or fishing mortality is constant, the last being the assumption underlying the Baranov catch equation. These assumptions imply different dynamics, and only in special cases two of these assumptions can hold true simultaneously. Whether this happens is dictated by the concentration profile (i.e., the dependence of mean fish density where fishing takes place on total stock abundance). We show that the assumed seasonal progression of fishing and the type of the concentration profile have major implications for fishery dynamics as well as biological and economic consequences of fishing, calling for increased awareness of these overlooked assumptions of fishery dynamics. However, in many cases the Baranov catch equation serves as a good approximation, even when its assumption of constant fishing mortality is violated.

scholarly journals Behavioural adjustment of fish to temporal variation in fishing pressure affects catchability: an experiment with angled trout

2020 ◽  
Vol 77 (1) ◽  
pp. 188-193 ◽  
Author(s):  
Barbara Koeck ◽  
Magnus Lovén Wallerius ◽  
Robert Arlinghaus ◽  
Jörgen I. Johnsson
Keyword(s):  
Temporal Variation ◽  
Internal State ◽  
Empirical Support ◽  
Population Level ◽  
Theoretical Models ◽  
Fishing Effort ◽  
Threat Perception ◽  
Fishing Pressure ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
Catch Rates

In passive fisheries, such as angling, the fishing success depends on the ultimate decision of a fish to ingest the bait, based on an individual’s internal state, previous experience, and threat perception. Fish surviving capture by anglers are known to be less vulnerable, and catch rates usually quickly decline with increasing fishing effort. Previous theoretical models have thus suggested fishing closures as a means to recover responsiveness of fish to angling gear and maintain catch rates, yet empirical support remains limited. In a controlled replicated pond experiment, we evaluated the effects of temporal variation in fishing pressure on catch rates of rainbow trout (Oncorhynchus mykiss) by simulating short-term fishing closures. Fishing closures increased catch rates and population-level catchability by reducing threat perception at the population level and allowing released individuals to return to a vulnerable state. Our experimental results show that periodic fishing closures benefit catch rates but at the risk of aggravating the likelihood of overharvesting.

How useful is the ratio of fish density outside versus inside no-take marine reserves as a metric for fishery management control rules?

2011 ◽  
Vol 68 (2) ◽  
pp. 343-359 ◽  
Author(s):  
Elizabeth A. Babcock ◽  
Alec D. MacCall
Keyword(s):  
Fishery Management ◽  
Spatial Scales ◽  
Marine Reserves ◽  
Density Ratio ◽  
Relative Weight ◽  
Fishing Effort ◽  
Management Control ◽  
Fish Density ◽  
Control Rules ◽  
Stock Depletion

A management strategy evaluation (based on five species in the California, USA, nearshore fishery) of control rules that reduce relative fishing effort as a function of the ratio of fish density outside versus inside no-take marine reserves (as a measure of depletion) showed that although the control rules allowed effort to increase at first, in the long term, they were effective at maintaining spawning stock biomass and yield for all simulated species, including depleted ones. Scenarios with fish movement, illegal fishing in the reserve, or post-dispersal density dependence in recruitment required higher density ratio targets, such as 60% of mature fish or 80% of all fish, to avoid stock depletion. The effort allowed by multispecies density-ratio control rules depended on the relative weight given to more or less depleted species. High variability in recruitment or in monitoring data caused the allowable effort to fluctuate. Density-ratio control rules have the advantages that they require no historical data, they can be used at local spatial scales, and they adjust to changing environmental conditions.

scholarly journals Predicting the effects of area closures and fishing effort restrictions on the production, biomass, and species richness of benthic invertebrate communities

2006 ◽  
Vol 63 (5) ◽  
pp. 822-830 ◽  
Author(s):  
J.G. Hiddink ◽  
T. Hutton ◽  
S. Jennings ◽  
M.J. Kaiser
Keyword(s):  
Species Richness ◽  
North Sea ◽  
Fishery Management ◽  
Benthic Communities ◽  
Fishing Effort ◽  
Management Actions ◽  
The North ◽  
The North Sea ◽  
Effort Reduction ◽  
Positive Effect

AbstractTo effectively implement an Ecosystem Approach to Fisheries (EAF), managers need to consider the effects of management actions on the fishery and the ecosystem. Methods for assessing the effects on target stocks are generally well developed, but methods for assessing the effects on other components and attributes of the ecosystem are not. Area closures and effort controls are widely used fishery management tools that affect the distribution of fishing effort and may therefore have consequences for a range of species and habitats. An approach is developed to predict the effects of area closures and effort control on the biomass, production, and species richness of benthic communities in the North Sea. The redistribution of beam trawling effort as a result of management action was modelled with a random utility model, assuming that fishers selected fishing grounds on the basis of their knowledge of past catch rates. The effects of trawling on benthic invertebrates were predicted using a size-based model that accounted for differences in habitat among fishing grounds. Our simulations demonstrated that closures of different sizes and in different locations could have positive or negative effects on benthic communities. These predicted effects resulted from the trade-off between recovery in the closed areas and additional trawling effects in the open areas that arose from displaced fishing activity. In the absence of effort controls, closure of lightly fished areas had the strongest positive effect on benthic communities. Effort reduction also had a positive effect. Therefore, area closures in lightly fished areas, coupled with effort reduction, are expected to minimize the effects of fishing on benthic communities. As it was not possible to access full international data for the North Sea beam trawl fleet, the results of the analyses are illustrative rather than complete. Nevertheless, what is demonstrated is an effective approach for assessing the environmental consequences of fishery management action that can be used to inform management decision-making as part of an EAF.

scholarly journals The effects of seasonal processes on size spectrum dynamics

2016 ◽  
Vol 73 (4) ◽  
pp. 598-610 ◽  
Author(s):  
Samik Datta ◽  
Julia L. Blanchard
Keyword(s):  
Environmental Variability ◽  
Management Strategies ◽  
Growth Curves ◽  
Fishing Effort ◽  
Size Spectrum ◽  
Interspecies Interactions ◽  
Community Size ◽  
Modelling Framework ◽  
Batch Spawning ◽  
Similar Growth

The recent advent of dynamic size spectrum models has allowed the analysis of life processes in marine ecosystems to be carried out without the high complexity arising from interspecies interactions within dense food webs. In this paper, we use “mizer”, a size spectrum modelling framework, to investigate the consequences of including the seasonal processes of plankton blooms and batch spawning in the model dynamics. A multispecies size spectrum model is constructed using 12 common North Sea fish species, with growth, predation, and mortality explicitly modelled, before simulating both seasonal plankton blooms and batch spawning of fish (using empirical data on the spawning patterns of each species). The effect of seasonality on the community size spectrum is investigated; it is found that with seasonal processes included, the species spectra are more varied over time, while the aggregated community spectrum remains fairly similar. Growth of seasonally spawning mature individuals drops significantly during peak reproduction, although lifetime growth curves follow nonseasonal ones closely. On analysing properties of the community spectrum under different fishing scenarios, seasonality generally causes more varied spectrum slopes and lower yields. Under seasonal conditions, increasing fishing effort also results in greater temporal variability of fisheries yields due to truncation of the community spectrum towards smaller sizes. Further work is needed to evaluate robustness of management strategies in the context of a wider range of seasonal processes and behavioural strategies, as well as longer term environmental variability and change.

scholarly journals Effects of scallop dredging on macrobenthic communities in west Iceland

2006 ◽  
Vol 63 (3) ◽  
pp. 434-443 ◽  
Author(s):  
Elena Guijarro Garcia ◽  
Stefán Áki Ragnarsson ◽  
Hrafnkell Eiríksson
Keyword(s):  
Benthic Community ◽  
Stock Assessment ◽  
Benthic Communities ◽  
Fishing Effort ◽  
Early Years ◽  
Total Catch ◽  
Macrobenthic Communities ◽  
Modiolus Modiolus ◽  
Cucumaria Frondosa

Abstract Effects of scallop dredging on benthic communities in Breidafjordur, west Iceland, were investigated by analysing bycatch data from scallop stock assessment surveys and effort data from the commercial scallop fishery. Bycatch constituted 28% of the total catch, with eight benthic macrofaunal taxa alone making up nearly 98% of the bycatch. Modiolus modiolus and Cucumaria frondosa dominated in terms of abundance and biomass in most of the study area regardless of intensity of fishing effort, although both have been identified as sensitive to fishing in other studies. The macrofaunal benthic community in Breidafjordur consisted mostly of hard-shelled molluscs, holothurians, crabs, and starfish. Emerging epifauna was absent in the samples taken since 1993. These results suggest that our study was carried out within an already altered community that would have suffered the greatest impact during the early years of the scallop fishery. However, the available data are not enough to endorse this assumption with complete certainty.

scholarly journals Bioeconomic Approach for Assessing Status of Trawl Fishery in the Straits of Malacca

2021 ◽  
Vol 34 (4) ◽  
Author(s):  
HOONG SANG WONG ◽  
◽  
CHEN CHEN YONG ◽  
AZMAH OTHMAN
Keyword(s):  
Fishery Management ◽  
Statistical Tests ◽  
Fishing Effort ◽  
Current Status ◽  
Fish Stock ◽  
Base Case ◽  
Current Effort ◽  
Price Inflation ◽  
Trawl Fishery ◽  
Straits Of Malacca

The Straits of Malacca provides half of Malaysia’s total marine fish and seafood supply. Due to depleted fish stock, the Malaysian Government has established a comprehensive legal framework to reduce overfishing in the Straits over the last five decades. However, there are limited scientific studies on the current status of stock recovery. This paper aims to use bioeconomic approach to determine the current trawl fishery status in the Straits. Various statistical tests showed that the Clarke-Yoshimoto-Pooley model was better than the Schnute model in predicting and thus used to estimate the crucial bioeconomic parameters. The current yield and standardised effort of 239,692 tonnes and 931,692 standard fishing days were very close to the estimated biological maximum sustainable yield (239,915 tonnes) and above 18 % of the standardised effort (763,649 standard fishing days) to achieve it. The maximum economic yield was estimated at 201,542 tonnes while the corresponding standardised effort was 396,799 standard fishing days indicating serious economic overfishing in the Straits. If the current effort can be reduced by 57 %, fish biomass and economic rent will increase by 97 % and 835 %, respectively. A price sensitivity analysis predicted that demand-pull fish price inflation could exacerbate the overfishing problem, particularly under unrestrained environment. A 50 % increase in price could lead to a 132 % increase in fishing effort from the base case. The findings of this paper provide valuable insights for fishery managers to refine their existing fishery management program to achieve sustainable fishery for the future.

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