Marine Trophic Index Research Articles

Once upon a century, the Egyptian Mediterranean fisheries (1920–2019), as affected by ‘fishing down’ and climate change

Fishing has been practiced in Egypt for several millennia in the Nile and various lakes, the Mediterranean, and the Red Sea. Here, the marine fisheries catch from the area corresponding to Egypt's current Exclusive Economic Zone in the Mediterranean were re-estimated for the shorter period from 1920 to 2019. This study covers reported and formerly unreported commercial and non-commercial, small- and large-scale fisheries catches and estimated discards. Given that the Food and Agriculture Organization (FAO) has been publishing annual fisheries statistics only since 1950, the comparison of reconstructed marine catch data to the FAO-reported catch data covers only the period from 1950 to 2019. Reconstructed marine fisheries catches for the Egyptian Mediterranean EEZ for 1950–2019 were about 1.3 times the reported catch by the FAO on behalf of Egypt. This discrepancy is due to a combination of elements, mainly unreported commercial industrial and artisanal catches and industrial discards.Several events have drastically affected the Mediterranean marine fisheries of Egypt, such as the opening of the Suez Canal, the Aswan High Dam, and, more recently, the Egyptian Revolution of 2011. Climate change has also influenced the overall productivity as well as the species composition of the catch. The Mean Temperature of Catch (MTC) from the Mediterranean Egyptian waters has increased by an annual average of 0.07 °C per year since 1987. The Marine Trophic Index (MTI) showed that ‘fishing down’ has occurred in Egypt's Mediterranean waters since the early 1970s.The dataset provided by this study can be applied to catch-based indicators to better assess the Egyptian Mediterranean fish stocks. This would help improve fisheries management in the region and ensure the sustainability of the Egyptian Mediterranean fisheries.

Catch trends of bottom trawl fauna with an emphasis on prawns and stomatopods, off Goa, India

Catch trends of bottom trawl fauna off Goa, India were investigated at fortnightly intervals from February 2006 – May 2008 with the exception of June – October months (monsoon). Inter-comparison of faunal abundance data obtained during February to April months of 2006, 2007 and 2008 indicated that abundance during 2006 and 2008 were significantly higher as compared to 2007. Available fish landing data for the region also corroborated this trend. The dominance of sub-adults among stomatopods during post-monsoon season (November – January), juveniles and sub-adults among prawns during pre-monsoon (February – May), indicated recruitment to the fishery. Comparison with 40-year-old published data indicated significant reduction in the overall yield (P = 0.043; α = 0.05). Additionally, yields of 12 out of 15 fish groups across the demersal trophic spectrum decreased significantly (P = 0.031; α = 0.05). However, catches of miscellaneous species increased 17 times, and were dominated by pufferfishes. The profusion of pufferfish is attributed to the perennial breeding habit of these fishes combined with increased removal of potential predators such as sharks and catfishes. Marine Trophic Index (MTI) and Fishing-in-Balance Index (FiB) decreased at rates of 0.017 and 0.016 per decade, respectively, implying sustained fishing pressure over the next few decades that could lead to potential trophic cascade and dominance of resilient opportunistic species such as puffers.&nbsp

Investigating Fishing Impacts in Nigerian Coastal Waters Using Marine Trophic Index Analyses

AbstractIn Nigerian coastal waters (NCW), fishing has increased steadily over the last seven decades. Artisanal fisheries cover the entire 850‐km length of the coast, where over 1 million fishermen exploit estuarine and oceanic resources up to 40 m deep, and approximately 250 industrial trawlers target fish resources in deeper waters beyond the first 9.26 km (5 nautical miles) from shore. We investigated the hypothesis that growth in fishing effort will increase impacts on coastal fish stocks, as reflected by significant reductions in the mean trophic level (MTL) and maximum mean length of the catch and an increase in the fishing‐in‐balance index. Our analyses are based on a 60‐year time series from 1950 to 2010 (obtained from the Sea Around Us Project; www.seaaroundus.org). Results showed that the impacts of fishing in NCW are high. The sustained increases in landings from the 1970s to the 2000s have resulted in less productive coastal fisheries, a reduction in the MTL of the catch (which might mean reduced biodiversity), a reduction of average size in the fisheries, and the need to expand further into deeper waters to maintain catch levels. This research contributes to fisheries ecology by furthering our understanding of coastal fisheries and their impacts on marine biodiversity.

Evaluating the specificity of ecosystem indicators to fishing in a changing environment: A model comparison study for the southern Benguela ecosystem

Ecological indicators used to monitor fishing effects in the context of climate change and variability need to be informative to enable effective ecosystem-based fisheries management. We evaluated the specificity of the response of ecosystem indicators to different fishing and environmental pressure levels using Ecosim and Atlantis ecosystem models for the southern Benguela ecosystem. Three fishing strategies were modelled to represent a variety of ways of targeting fishing within an ecosystem: one focused on low trophic levels (i.e. forage species), another on higher trophic levels (i.e. predatory fish) and a third tested fishing pressure across the full range of potentially exploitable species. Two types of environmental change were simulated for each fishing mortality scenario – random environmental variability and directional climate change. The specificity of selected ecological indicators (mean trophic level of the community, proportion of predatory fish, biomass/landings, mean intrinsic vulnerability and marine trophic index) was evaluated for different combinations of fishing strategy, fishing mortality and both types of environmental change. While there were mostly large differences in indicator values computed from the Atlantis and Ecosim models, the specificity of the ecological indicators considered under changing climate generally corresponded between the two models. Certain indicators (i.e. mean trophic level of the community) were less specific in detecting effects of fishing in the southern Benguela for some of the three fishing strategies modelled (i.e. high trophic level fishing strategy) under climate change. This helped refine the most appropriate indicator set for our system, reflecting the focus of a particular fishing strategy, and improved confidence in the suitability of these indicators for monitoring fishing effects in the Southern Benguela.

The analysis of convergence in ecological indicators: An application to the Mediterranean fisheries

Ecological indicators are increasingly used to examine the evolution of natural ecosystems and the impacts of human activities. Assessing their trends to develop comparative analyses is essential. We introduce the analysis of convergence, a novel approach to evaluate the dynamic and trends of ecological indicators and predict their behavior in the long-term. Specifically, we use a non-parametric estimation of Gaussian kernel density functions and transition probability matrix integrated in the R software. We validate the performance of our methodology through a practical application to three different ecological indicators to study whether Mediterranean countries converge towards similar fisheries practices. We focus on how distributions evolve over time for the Marine Trophic Index, the Fishing in Balance Index and the Expansion Factor during 1950–2010. Results show that Mediterranean countries persist in their fishery behaviors throughout the time series, although a tendency towards similar negative effects on the ecosystem is apparent in the long-term. This methodology can be easily reproduced with different indicators and/or ecosystems in order to analyze ecosystem dynamics.

Ecosystem indicators—accounting for variability in species’ trophic levels

Trophic level (TL)-based indicators are commonly used to track the ecosystem effects of fishing as the selective removal of organisms from the food web may result in changes to the trophic structure of marine ecosystems. The use of a fixed TL per species in the calculation of TL-based indicators has been questioned, given that species’ TLs vary with ontogeny, as well as over time and space. We conducted a model-based assessment of the performance of fixed TL-based indicators vs. variable TL-based indicators for tracking the effects of fishing pressure. This assessment considered three TL-based indicators (the trophic level of the landed catch (TLc), the marine trophic index (MTI) and the trophic level of the surveyed community (TLsc)), three fishing scenarios that targeted specific model groups (the low TL scenario (LTL), the high TL scenario (HTL) and a scenario encompassing broad-scale exploitation (ALL)) and ten contrasting marine ecosystems with four types of ecosystem modelling approaches that differ in their structure and assumptions. Results showed that, overall, variable TL-based indicators have a greater capacity for detecting the effects of fishing pressure than fixed TL-based indicators. Across TL-based indicators, TLsc displayed the most consistent response to fishing whether fixed or variable species' TLs were used, as well as the highest capacity for detecting fishing effects. This result supports previous studies that promote the use of survey-based indicators over catch-based indicators to explore the impacts of fishing on the structure of marine ecosystems. Across fishing scenarios, the low trophic level fishing scenario (LTL) resulted in the lowest consistency between fixed and variable TL-based indicator responses and the lowest capacity of TL-based indicators for detecting fishing effects. Overall, our results speak to the need for caution when interpreting TL-based indicator trends, and knowledge of the broader context, such as fishing strategies and exploitation history.

New trophic indicators and target values for an ecosystem-based management of fisheries

In the present study, we tested five trophic indicators and we demonstrated their usefulness to assess the environmental status of marine ecosystems and to implement an ecosystem approach to fisheries management (EAFM). The tested indicators include the slope of the biomass spectrum, the mean trophic level (MTL), the marine trophic index (MTI) and two newly developed indicators, the high trophic level indicator (HTI) and the apex predator indicator (API). Indicators are compared between current state and potential reference situations, using as case studies: the Celtic Sea/Bay of Biscay, North Sea and English Channel ecosystems. Trophic spectra are obtained from Ecopath models while reference situations are estimated, simulating with EcoTroph and Ecosim different fishing pressures including three candidate scenarios for an EAFM. Inter-ecosystems assessments are done using Ecopath models, simulations outputs and scientific surveys data to assess the current states of the studied ecosystems, contrast the reference situations and analyze the responses of all indicators. Sensitivity analyses are also conducted on the main simulation parameters to test the robustness of the chosen indicators. Ecosystems specific targets for EAFM are proposed for the five trophic indicators estimated from whole-ecosystem models, while in the Celtic Sea/Bay of Biscay ecosystem targets are proposed for the MTL (=3.85) and HTI (48%) estimated from standard bottom-trawl surveys. The HTI is proposed to be relevant for survey data and the API is recommended using whole-ecosystem models. We conclude that HTI and API show trends in ecosystems health better than MTI.

Ecological indicators to capture the effects of fishing on biodiversity and conservation status of marine ecosystems

IndiSeas (“Indicators for the Seas”) is a collaborative international working group that was established in 2005 to evaluate the status of exploited marine ecosystems using a suite of indicators in a comparative framework. An initial shortlist of seven ecological indicators was selected to quantify the effects of fishing on the broader ecosystem using several criteria (i.e., ecological meaning, sensitivity to fishing, data availability, management objectives and public awareness). The suite comprised: (i) the inverse coefficient of variation of total biomass of surveyed species, (ii) mean fish length in the surveyed community, (iii) mean maximum life span of surveyed fish species, (iv) proportion of predatory fish in the surveyed community, (v) proportion of under and moderately exploited stocks, (vi) total biomass of surveyed species, and (vii) mean trophic level of the landed catch. In line with the Nagoya Strategic Plan of the Convention on Biological Diversity (2011–2020), we extended this suite to emphasize the broader biodiversity and conservation risks in exploited marine ecosystems. We selected a subset of indicators from a list of empirically based candidate biodiversity indicators initially established based on ecological significance to complement the original IndiSeas indicators. The additional selected indicators were: (viii) mean intrinsic vulnerability index of the fish landed catch, (ix) proportion of non-declining exploited species in the surveyed community, (x) catch-based marine trophic index, and (xi) mean trophic level of the surveyed community. Despite the lack of data in some ecosystems, we also selected (xii) mean trophic level of the modelled community, and (xiii) proportion of discards in the fishery as extra indicators. These additional indicators were examined, along with the initial set of IndiSeas ecological indicators, to evaluate whether adding new biodiversity indicators provided useful additional information to refine our understanding of the status evaluation of 29 exploited marine ecosystems. We used state and trend analyses, and we performed correlation, redundancy and multivariate tests. Existing developments in ecosystem-based fisheries management have largely focused on exploited species. Our study, using mostly fisheries independent survey-based indicators, highlights that biodiversity and conservation-based indicators are complementary to ecological indicators of fishing pressure. Thus, they should be used to provide additional information to evaluate the overall impact of fishing on exploited marine ecosystems.

Landing profiles of Portuguese fisheries: assessing the state of stocks

Long-term trends in Portuguese fisheries landing profiles of biodiversity, assemblage composition, trophic groups and marine trophic index (1950–2009) were studied to understand the evolution of the fisheries from an ecological viewpoint and evaluate the effects of fisheries on stocks. The number of species landed has increased considerably since the 1980s. This indicates an expansion of the fisheries and also a better use of the marine biodiversity for redistributing effort. Changes in the ecological composition of fisheries catches have occurred since the 1950s, with a significant shift in the middle 1980s (anchor point). Deep-sea resources and higher trophic levels (cephalopods, large benthopelagics, flatfishes, demersal invertebrates, small-medium and large rays, medium bathydemersal, shrimps, small benthopelagics large sharks) have increased while traditional commercial species captured by nearshore fisheries (medium and small pelagics) have decreased. Despite the decreasing trend in catches since 1988, the marine trophic index (MTI = 3.04) increased by approximately 0.2 units per decade (MTI in 2009 = 3.46). The number of collapsed, overexploited and fully exploited stocks has increased considerably over the last 20 years (>50%). Overall, the data indicate that redistributing fishing effort and targeting of deep-sea resources may have been driven by depletion of inshore fishery stocks, which signals concern for the fishery. Marine biodiversity indexes and ecological structure of landings profiles should be considered by fishery managers when redefining new marine fisheries policy.

Democracy, development and the marine environment – A global time-series investigation

Is democracy favorable or adverse for the management of marine resources? While some studies find democracy to increase the likelihood of achieving sustainable development, others propose that democracy rather has negative effects on the environment. This paper contributes explicitly to this debate, but also adds insights from research arguing that the effects of democracy are conditioned by surrounding institutions. Building on this literature, we argue that the way democracy works – whether it is an instrument for collective action beneficial to the environment or an instrument for patronage and clientelism – depends on levels of economic development. The overall objective of the article is to test this proposition empirically. Employing time-series cross-section analysis and using Marine Trophic Index as a proxy for the health of marine ecosystems, we investigate the impact of democracy on the marine environment in a global sample from 1972 to 2006. The analysis provides interesting insights regarding the conditional role of economic development. We report negative effects of democracy in low income settings, but find that this pattern is reversed when economic development has reached a certain threshold. Finally, we discuss how democracy affects the prospects for sustainable development and based on our conclusions offer suggestions for future research.

Region-based MTI: resolving geographic expansion in the Marine Trophic Index

The Marine Trophic Index (MTI), which tracks the mean trophic level of fishery catches from an ecosystem, generally, but not always, tracks changes in mean trophic level of an ensemble of exploited species in response to fishing pressure. However, one of the disadvantages of this indicator is that declines in trophic level can be masked by geographic expansion and/or the development of offshore fisheries, where higher trophic levels of newly accessed resources can overwhelm fishing-down effects closer inshore. Here, we show that the MTI should not be used without accounting for changes in the spatial and bathymetric reach of the fishing fleet, and we develop a new index that accounts for the potential geographic expansion of fisheries, called the region-based MTI (RMTI). To calculate the RMTI, the potential catch that can be obtained given the observed trophic structure of the actual catch is used to assess the fisheries in an initial (usu- ally coastal) region. When the actual catch exceeds the potential catch, this is indicative of a new fishing region being exploited. The MTI of the new region can then be calculated, and subsequent regions are determined in a sequential manner. This method improves upon the use of the Fish- ing-in-Balance (FiB) index in conjunction with the original MTI calculated over the whole time series because assumptions of fleet and stock stationarity over the entire time series and geo- graphic area are removed. We illustrate the utility of the RMTI with simulated examples and actual data, and generalize these results.

Changes in the marine trophic index of Chinese marine area

Using the fishery catches and landings data from Food and Agriculture Organization of the United Nations (FAO) Fishery Statistics (1950 to 2011) for 129 marine species, we analyzed changes in the trophic index of captured species in China (including 4 sea areas: Mainland, Taiwan, Hong Kong and Macau). The results showed the following: the marine trophic index remained stable from 1950 to 1974, fluctuating around 3.45, then declined to 3.35 during the period 1975-1978, declined again sharply to 3.25 between 1982 and 1987, remained stable in the following 10 years, and then increased gradually to 3.34 from 1997 to 2011. Comparing to global marine trophic index, China's marine trophic index was higher than the global level be- fore 1984, but became lower after 1984. Comparing the contributions of the 4 main biological groups used in the calculation of the index showed that fish species contributed the mostly at 73.1-85.8%, crustaceans con- tributed 9.2-15.5%, molluscs contributed 3.3-11.6%, and other invertebrates contributed less than 1.8%. The general decline we observed in China's marine trophic index is associated with shifts in fishery catches from benthic fishes with a long lives and high trophic levels, to invertebrates and pelagic fishes with short lives and low trophic levels. Increasing Chinese marine trophic index from 1997 to 2011 may be attributed to a se- ries of fishery management countermeasures, including new fishing permits regulations, closed fishing sea- sons, zero and negative growth plans for marine fishery catches and landings, artificial breeding and

Horizontal and vertical resource dilemmas in natural resource management: the case ofAfrican fisheries

AbstractThe world's fisheries are under severe pressure. Yet, according to the marine trophic index, the health and stability of marine ecosystems vary greatly across countries. The argument developed and tested in this article holds that some of the sources of this variation can potentially be derived from differences in the character of two fundamental relationships in society – a horizontal one between resource users and a vertical relationship between the government and the resource users. The empirical analysis focuses on sub‐Saharan Africa and finds that levels of ethnic and linguistic heterogeneity and levels of democracy in the year that each country declared its exclusive economic zone have a close relationship with ensuing marine exploitation patterns.

Fishing down, fishing through and fishing up: fundamental process versus technical details

Fishing through, fishing up (i.e. the observation that mean trophic levels (MTLs) of catches are increasing with time) and the question of agreement between MTL from catches and surveys have been used to question fishing down the marine food web as well as the use of the marine trophic index as an effective ecosystem indicator. This has evolved into a crucial debate in marine ecology and fisheries management. We believe that fishing down, fishing through and fish- ing up the food web are not incompatible but only appear so because of confusion. Fishing down is an ecological process, which can be expected to either occur or not, i.e. it is a hypothesis which can be falsified and replaced by an alternative hypothesis that must also rely on ecological princi- ples (rather than technicalities). In contrast, fishing through and fishing up reflect technical issues related to biases in the available data and/or to fishing behaviour and thus do not falsify fishing down. The latter could be falsified if, for instance, in an ecosystem subjected to intense fishing, the biomasses of all or several large predators increase and these increases go along with an increase in their mean lengths for an extended period of time. Thus, MTL remains one of the most opera- tional indices available for testing fishing down. It is without doubt that, in various cases, MTL will not be effective because of various technical confounding factors, which can be clarified by local experts. Undoubtedly, MTL can be misused, usually when confounding effects cannot be properly disentangled, and thus it must be used and interpreted with caution.

Review of multispecies indices for monitoring human impacts on biodiversity

Biodiversity has been recognized as one of the key components of environmental sustainability. Assessment of biodiversity trends and progress toward targets requires effective and sound indicators. In our article, we review and compare the leading multispecies biodiversity indices used in global and regional assessments. We reviewed basic characteristics of these aggregated and composite biodiversity indicators and evaluated them with regard to their ecological performance, policy relevance and other accounting aspects. Indices analyzed include species and populations based indicators, such as Living Planet Index and Red List Index, as well as ecosystem based indicators like Natural Capital Index and Biodiversity Intactness Index. We also include measures of ecological integrity such as Marine Trophic Index and Index of Biotic Integrity. Indicators analyzed differ in both their ecological focus, baselines, basic units or policy use. Multispecies biodiversity indices illustrate prevailingly negative trends in the state of nature as a result of human induced pressures, especially land cover change. Biodiversity loss is therefore not decoupled from socioeconomic progress. We show that current indicators include a balanced mix of important biodiversity aspects and have some policy resonance. Leading biodiversity indices should be further promoted and integrated into monitoring, modelling and decision-making frameworks.

Trophic indicators to measure the impact of fishing on an exploited ecosystem

There is currently a global call for more use of an ecosystem approach to fisheries management (EAFM) to provide a holistic view of ecosystem-fisheries interactions. Trophic indicators could therefore be used to support the implementation of an EAFM by providing information on the state of the ecosystem. In this paper we propose a set of indicators such as the marine trophic index (MTI), the fishing in balance (FiB), the cut marine trophic index (cutMTI) and the pelagic/demersal index (P/D) to assess the dynamics and the trophic changes in the Black Sea large marine ecosytem from 1970 to 2005. Our analysis shows a heavily exploited ecosystem where overfishing and anthropogenic eutrophication are probably responsible. The decline of the MTI, cutMTI and FiB together with the rising trend of the P/D index could be interpreted as a fishing down marine food web process with a strong decrease in abundance of high trophic level species and a considerable increase of low trophic level species.

Priceless prices and marine food webs: Long-term patterns of change and fishing impacts in the South Brazil Bight as reflected by the seafood market

The lack of market variables in fishery systems (i.e., prices and quantities) has often been cited as one reason for the particular difficulty of understanding whole marine ecosystem change and its management under a broader ecosystem perspective. This paper shows the results of efforts to tackle this problem in the South Brazil Bight by compiling and analyzing in-depth an unprecedented 40-year database from the region’s largest wholesale seafood market, based in the megacity of São Paulo. Fishery landings and market values for the period 1968–2007 were analyzed primarily by updated trophic level classes and multispecies indicators including the (1) marine trophic index (MTI), (2) weighted price, and (3) log relative price index (LRPI) which relates prices and trophic levels. Moreover, an inferential analysis of major seafood category statistical trends in market prices and quantities and their positive and negative correlations was undertaken. In general, these market trends contributed substantially to identifying and clarifying the changes that occurred. Considerations of the behavior of demand, supply and markets are included. In particular, while the MTI did not support a “fishing down the marine food web” hypothesis, other indicators did show the continued scarcity of major high trophic level categories and fisheries target species. Overall, the results indicate that the analysis of fishery landings, or of certain other indicators alone, can mask real changes. Rather, a joint ecological–econometric analysis provides better evidence of the direction of ecosystem pressures and stock health. This method for detecting market changes across the food web may be particularly helpful for systems considered data-poor but where fish market data have been archived. This study further elucidates historical changes and fishing impacts in the South Brazil Bight ecosystem.

National Indicators Show Biodiversity Progress

In their Report “Global biodiversity: Indicators of recent declines” (28 May, p. [1164][1]), S. H. M. Butchart and colleagues commented that on a global scale there is little evidence that the rate of biodiversity decline is slowing and some evidence that it is increasing. However, there are some encouraging stories at national levels. For instance, the Chinese government has implemented biodiversity conservation action plans. The proportion of China's gross domestic product invested in environmental pollution control and forestry conservation has increased since 1990 and exceeded 1% since 2001; the number of nature reserves was 32 times the number in 1978, and the area devoted to reserves was 120 times the area in reserves in 1978 ([ 1 ][2]). There is more good news: Some indicators of pressures on biodiversity show declining trends. The total discharge of chemical oxygen demand and the amount of sulfur dioxide in waste gas, two nationally targeted pollutants, decreased 9.66 and 13.14%, respectively, as compared with that of 2005 ([ 2 ][3]). The discharge of toxic and harmful pollutants in wastewater, the emission intensity of chemical oxygen demand of key industries, the emission of soot dust and industrial dust in waste gases, and the discharge of solid wastes decreased annually 12.24, 21.62, 5.16, and 16.89% since 1998, respectively ([ 1 ][2]). Some indicators of the state of biodiversity showed recovering trends. The annual average net primary productivity, including forest resources as well as the area and growing stock of natural forests, has been increasing in the past two decades ([ 1 ][2], [ 3 ][4]); there is also a steady increase in the Marine Trophic Index from 1997 until now ([ 1 ][2]). Although substantial progress toward the 2010 target was made ([ 4 ][5]), we agree that China still faces severe environmental pressures, because total pollutant emissions are still high, and trends toward the loss of habitats, threatened species, and genetic resources are not effectively checked ([ 1 ][2]). 1. [↵][6] 1. H. G. Xu 2. et al ., BioScience 59, 843 (2009). [OpenUrl][7][CrossRef][8][Web of Science][9] 2. [↵][10] Ministry of Environmental Protection of China ([www.mep.gov.cn/zhxx/hjyw/201005/t20100514_189487.htm][11] [in Chinese]). 3. [↵][12] 1. Z. Q. Gao, 2. J. Y. Liu , Chin. Sci. Bull. 53, 317 (2008). [OpenUrl][13][CrossRef][14] 4. [↵][15] Ministry of Environmental Protection of China, China's Fourth National Report on Implementation of the Convention on Biological Diversity (China Environmental Sciences Press, Beijing, 2009). [1]: /lookup/doi/10.1126/science.1187512 [2]: #ref-1 [3]: #ref-2 [4]: #ref-3 [5]: #ref-4 [6]: #xref-ref-1-1 View reference 1 in text [7]: {openurl}?query=rft_id%253Dinfo%253Adoi%252F10.1525%252Fbio.2009.59.10.6%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [8]: /lookup/external-ref?access_num=10.1525/bio.2009.59.10.6&link_type=DOI [9]: /lookup/external-ref?access_num=000271420000007&link_type=ISI [10]: #xref-ref-2-1 View reference 2 in text [11]: http://www.mep.gov.cn/zhxx/hjyw/201005/t20100514_189487.htm [12]: #xref-ref-3-1 View reference 3 in text [13]: {openurl}?query=rft_id%253Dinfo%253Adoi%252F10.1007%252Fs11434-008-0064-4%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [14]: /lookup/external-ref?access_num=10.1007/s11434-008-0064-4&link_type=DOI [15]: #xref-ref-4-1 View reference 4 in text

Fishing down Brazilian marine food webs, with emphasis on the east Brazil large marine ecosystem

An analysis of Brazilian marine fisheries catch data covering the years 1978–2000 is conducted with emphasis on testing for the occurrence of the ‘fishing down the marine food web’ phenomenon in the East Brazil Large Marine Ecosystem (LME). The results show that this phenomenon becomes apparent only after national data are disaggregated into smaller entities, as exemplified here for seven states of Northeastern Brazil (corresponding to the East Brazil LME). Once the disaggregation was performed, the decline of trophic level occurring through most of Northeastern Brazil was shown to occur at a rate of 0.16 trophic level per decade, one of the highest rates of trophic level decline documented in the world. Also, fishing ‘through’ the food web, proposed as an alternative to fishing down, did not occur. Overall, this indicates that the Marine Trophic Index (i.e., the mean trophic level of the catch) is indeed a robust indicator of biodiversity loss, as envisaged by the Convention of Biological Diversity, and that the marine biodiversity of the East Brazil LME is being eroded.

The effect of season and sex on trophic levels of marine fishes

The diet of 76 species from Greek waters (north Aegean Sea) was examined for the determination of trophic level by species, season and sex. Trophic level estimates were derived from TrophLab software based on collected stomach content data. Such estimates are important for the implementation of marine management indicators, such as the marine trophic index. The mean ±s.e. difference between minimum and maximum trophic levels among seasons within species was 0·45 ± 0·04 and for 28·8% of the species this difference was larger than the corresponding s.e. of the trophic level of the pairs of seasons examined. Depending on which seasonal trophic level (i.e. autumn, winter, spring or summer) was used for assigning a species into a functional trophic group 33·9 and 8·5% of the species changed one and more than one group, respectively. Finally, the mean ±s.e. absolute difference of male and female trophic level was 0·18 ± 0·02, and only for 6·6% of the species this difference was larger than the s.e. of trophic level for each sex separately. Depending on the trophic level used for assigning the species into a functional group (i.e. male v. female), only 6·6 and 3·2% of the species changed one and more than one groups, respectively. It is therefore clear that all measures used in this study indicated that the effect of season on trophic level estimates was higher, compared to that of sex, the latter being of minor importance to feeding studies. Hence, future effort on stomach content analysis should focus on the examination of seasonal, small to moderate sample sizes.