252 research outputs found
Competition between fisheries and marine mammals for prey and primary production in the Pacific Ocean
The degree of competition between fisheries and marine mammals in the Pacific Ocean was estimated for 7 statistical areas defined by the Food and Agriculture Organization of the United Nations (FAO). Catch statistics compiled from FAO sources show that the amount of fish caught in the Pacific Ocean rose from 2 million tons in the late-1940s to over 50 million tons in the early-1990s. Recent stagnation and declines occurring in some areas of the Pacific suggest that Pacific fisheries cannot continue to expand as they had previously.
Based on estimates of population size, total biomass and daily consumption rates, it was estimated that the 84 species of marine mammals inhabiting the Pacific Ocean consume about three times as much food as humans harvest. A large fraction (>60%) of the food caught by marine mammals consisted of deep sea squids and very small deep sea fishes not harvestable by humans, thus limiting the extent of direct competition between fisheries and marine mammals. Moreover, the most important consumers of commercially exploited fish are other predatory fish, not marine mammals.
Although direct competition between fisheries and marine mammals for prey appears rather limited, there may be considerable indirect competition for primary production. The primary production required to sustain marine mammals in each of the 7 FAO areas varies within a narrow range, suggesting that the diversity and abundance of marine mammals may have slowly evolved to fully exploit their niche and maximize their use of available primary production. This contrasts with the rapid expansion of fisheries and their relatively recent dependence on primary production, which may have led to what we call 'food web competition'
Descripción del gran ecosistema marino del noreste de Brasil usando un modelo trófico
The objective of this study was to describe the marine ecosystem off northeastern Brazil. A trophic model was constructed for the 1970s using Ecopath with Ecosim. The impact of most of the forty-one functional groups was modest, probably due to the highly reticulated diet matrix. However, seagrass and macroalgae exerted a strong positive impact on manatee and herbivorous reef fishes, respectively. A high negative impact of omnivorous reef fishes on spiny lobsters and of sharks on swordfish was observed. Spiny lobsters and swordfish had the largest biomass changes for the simulation period (1978-2000); tunas, other large pelagics and sharks showed intermediate rates of biomass decline; and a slight increase in biomass was observed for toothed cetaceans, large carnivorous reef fishes, and dolphinfish. Recycling was an important feature of this ecosystem with low phytoplankton-originated primary production. The mean transfer efficiency between trophic levels was 11.4%. The gross efficiency of the fisheries was very low (0.00002), probably due to the low exploitation rate of most of the resources in the 1970s. Basic local information was missing for many groups. When information gaps are filled, this model may serve more credibly for the exploration of fishing policies for this area within an ecosystem approach.El objetivo de este estudio fue describir el ecosistema marino del noreste de Brasil. Se construyó un modelo trófico para representar la década de los 70 usando el modelo Ecopath con Ecosim. El impacto de la mayor parte de los 41 grupos funcionales fue pequeño, probablemente debido a lo intricado de la matriz trófica. No obstante, las fanerógamas marinas y las macroalgas tuvieron un fuerte impacto positivo sobre los manatíes y los peces recifales herbívoros, respectivamente. Los peces recifales omnívoros tuvieron un impacto negativo sobre las langostas espinosas, y los tiburones sobre el pez espada. Las langostas espinosas y el pez espada presentaron los mayores cambios de biomasa durante el período de simulación (1978-2000); las biomasas de atunes, otros grandes pelágicos y tiburones sufrieron disminuciones en ese período; se observó un ligero aumento en la biomasa de los odontocetos, de los grandes peces recifales carnívoros y de la lamprea. El reciclaje de materia orgánica por parte del fitoplancton fue importante en este ecosistema con baja productividad primaria. La eficiencia de transferencia media entre los niveles tróficos fue de 11.4%. La eficiencia bruta de la pesca fue muy baja (0.00002), probablemente debido a la baja tasa de explotación de la mayor parte de los recursos pesqueros en la década de los 70. No fue posible obtener las informaciones básicas locales para muchos grupos. Se estima que cuando se generen y estén disponibles más datos específicos locales, el modelo aquí elaborado puede ser mejor usado para el análisis de políticas pesqueras para esta área con una aproximación ecosistémica
Modelling the Mediterranean marine ecosystem as a whole: addressing the challenge of complexity
An ecosystem modelling approach was used to understand and assess the whole 16 Mediterranean marine ecosystem structure and functioning. In particular, two food web 17 models for the 1950s and 2000s periods were built to investigate: 1) the main structural and 18 functional characteristics of the Mediterranean food-web during these time periods; 2) the key 19 species/functional groups and interactions; 3) the role of fisheries and its impact; and 4) the 20 ecosystem properties of the Mediterranean Sea in comparison with other European Regional 21 Seas. Results show that among all functional groups the highest trophic levels were observed 22 for marine mammals and large predatory fish. The ecosystem flows were mainly dominated by 23 lower trophic level organisms, as benthic invertebrates, zooplankton and phytoplankton while 24 small pelagic fish, mainly European sardines and anchovies, prevailed in terms of biomasses and 25 catches. Large pelagic fish, sharks and medium pelagic fish seemed to play a key role in the past 26
ecosystem, replaced in more recent year by large pelagic fish, benthopelagic and benthic 27 cephalopods. Fisheries showed large impacts on most living groups of the ecosystem in both 28 time periods. Also, when comparing the Mediterranean to the other European Regional Seas, 29 the Mediterranean stood alone in relation to the type of flows driving the system and the 30 cycling indices, suggesting higher levels of community stress induced by intensive fishing 31 activities. In the near future, effort should be dedicated to implement spatial and temporal 32 dynamic simulations to evaluate the exploitation status of the Mediterranean Sea and explore 33 different management policies and future scenarios.JRC.H.1-Water Resource
A century of fish biomass decline in the ocean
Contribution to the Theme Section ‘Trophodynamics in marine ecology’.-- 12 pages, 7 figures, 3 tables, supplementary material https://doi.org/10.3354/meps10946We performed a global assessment of how fish biomass has changed over the last 100 yr, applying a previously developed methodology using ecological modeling. Our assessment built on more than 200 food web models representing marine ecosystems throughout the world covering the period from 1880 to 2007. All models were constructed based on the same approach, and have been previously documented. We spatially and temporally distributed fish biomasses delivered by these models based on fish habitat preferences, ecology, and feeding conditions. From these distributions, we extracted over 68000 estimates of biomass (for predatory and prey fishes separately, including trophic level of 3.5 or higher, and trophic level between 2.0 and 3.0, respectively), and predicted spatial-temporal trends in fish biomass using multiple regression. Our results predicted that the biomass of predatory fish in the world oceans has declined by twothirds over the last 100 yr. This decline is accelerating, with 54% occurring in the last 40 yr. Results also showed that the biomass of prey fish has increased over the last 100 yr, likely as a consequence of predation release. These findings allowed us to predict that there will be fish in the future ocean, but the composition of fish assemblages will be very different from current ones, with small prey fish dominating. Our results show that the trophic structure of marine ecosystems has changed at a global scale, in a manner consistent with fishing down marine food webs. © Inter-Research 2014This is a contribution from Sea Around Us, a scientific cooperation between the University of British Columbia (UBC) and the Pew Charitable trust. V.C. acknowledges support from the Natural Sciences and Engineering Research Council of Canada. M.C. was partially funded by the EC Marie Curie Career Integration Grant Fellowships to the BIOWEB project and the Spanish National Program Ramon y Cajal.Peer Reviewe
Brewer's spent grain, coffee grounds, burdock, and willow-four examples of biowaste and biomass valorization through advanced green extraction technologies
This paper explores the transformation of biowastes from food industry and agriculture into high-value products through four examples. The objective is to provide insight into the principles of green transition and a circular economy. The first two case studies focus on the waste generated from the production of widely consumed food items, such as beer and coffee, while the other two examine the potential of underutilized plants, such as burdock and willow, as sources of valuable compounds. Phenolic compounds are the main target in the case of brewer's spent grain, with p-coumaric acid and ferulic acid being the most common. Lipids are a possible target in the case of spent coffee grounds with palmitic (C16:0) and linoleic (C18:2) acid being the major fatty acids among those recovered. In the case of burdock, different targets are reported based on which part of the plant is used. Extracts rich in linoleic and oleic acids are expected from the seeds, while the roots extracts are rich in sugars, phenolic acids such as chlorogenic, caffeic, o-coumaric, syringic, cinnamic, gentisitic, etc. acids, and, interestingly, the high-value compound epicatechin gallate. Willow is well known for being rich in salicin, but picein, (+)-catechin, triandrin, glucose, and fructose are also obtained from the extracts. The study thoroughly analyzes different extraction methods, with a particular emphasis on cutting-edge green technologies. The goal is to promote the sustainable utilization of biowaste and support the green transition to a more environmentally conscious economy.info:eu-repo/semantics/publishedVersio
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Ecosystems at Risk: The Contribution of Ecosystem Approaches to Fisheries to Identify Problems and Evaluate Potential Solutions
The wide expanse of the sea, the inter-linkages among, and the productivity of its resources have until recently led most researchers to consider it unrealistic that humans could have more than local impact on marine ecosystems and their biodiversity. This perception is changing, however, as more evidence of the scale of impact becomes available. An enabling factor for this has been a change in focus from local-level studies to increased emphasis on meta-analysis of global or regional-level analysis of fisheries impact. Results include that the world’s total fish catches are no longer increasing, but rather have been decreasing over the last decade or more; that larger, predatory fishes (table fish) are becoming increasingly scarcer; and that we are appropriating the ocean shelves’ primary productivity to the same level as we are for terrestrial ecosystems. Ecosystems are being eroded in countries throughout the world, and though one might get the impression from the IUCN Red List that it is mainly a developed-country problem, it is alarming that the impact of severe overfishing may be at an even larger scale for developing countries. We describe aspects of the risks overfishing poses to marine ecosystems, and point out how ecosystem approaches to fisheries can be used to evaluate the potential impact of alternative fishing policy scenarios
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