scholarly journals Fishing destabilizes the biomass flow in the marine size spectrum

2011 ◽  
Vol 279 (1727) ◽  
pp. 284-292 ◽  
Author(s):  
M.-J. Rochet ◽  
E. Benoît
Keyword(s):  
Size Range ◽  
Prey Size ◽  
Size Spectrum ◽  
Small Fish ◽  
Marine Food Webs ◽  
Community Model ◽  
Size Diversity ◽  
Flow Oscillations ◽  
Marine Food ◽  
Fishing Impacts

Fishing impacts on marine food webs are predicted by simulations of a size spectrum community model. In this model, predation is determined by predator and prey size and abundance, and drives predator growth and prey mortality. Fishing amplifies temporal oscillations in the biomass flow. Oscillations appear at lower fishing intensity and have wider amplitude when fishing is selective (removes a narrow size range) and/or when large fish are targeted, than when fishing is more balanced (catching a larger size range) or when small fish are targeted. A novel index of size diversity is developed, and is shown to be sensitive to both fishing intensity and selectivity. To avoid unstable food web dynamics with potential harmful consequences for fisheries, limiting both fishing intensity and selectivity might be an appropriate exploitation strategy.

Measures of fish community size structure as indicators for stream monitoring programs

2020 ◽  
Vol 77 (5) ◽  
pp. 824-835
Author(s):  
Isaac A. Sutton ◽  
Nicholas E. Jones
Keyword(s):  
Land Use ◽  
Body Size ◽  
Power Law ◽  
Size Range ◽  
Size Structure ◽  
Size Spectrum ◽  
Community Size ◽  
Stream Monitoring ◽  
Lotic Ecosystem ◽  
Size Diversity

Characterization of community size structure presents an alternative to taxa-based approaches commonly applied to assess lotic ecosystem health. However, few studies have explored the relationship between community size structure and land use stresses in lotic systems. In the present study, we investigated use of metrics including mean body size, body size range, size diversity, size evenness, and the size spectrum slope as indicators of land use disturbance in streams. We also explored the effects of sampling intensity (one- versus three-pass electrofishing) on these size-based variables. We found significant decreases in size range and diversity with increased urban cover. In contrast, mean body size, size evenness, and size spectrum slopes were unrelated to variation in land use. Fewer than 25% of samples collected conformed to the power law model predicted for size distributions in aquatic ecosystems. However, increased departure from the power law form was related to agricultural cover and the use of three-pass electrofishing.

scholarly journals Role of Nanoplanktons in Marine Food-Webs

2015 ◽  
Vol 43 ◽  
pp. 38-47 ◽  
Author(s):  
Neelava Das ◽  
Ashish Pandey
Keyword(s):  
Aquatic Ecosystems ◽  
Size Range ◽  
Heterotrophic Nanoflagellates ◽  
Marine Food Webs ◽  
Living Biomass ◽  
Ecological Roles ◽  
The Subject ◽  
Marine Food ◽  
Bacterial Assemblages

Nanoplanktons are ubiquitous protozoan zooplankton in a size range of 2 to 20 μm, play key ecological roles in aquatic ecosystems. Heterotrophic nanoflagellates are distributed through the continental shelf and margin area of the oceans as well as deep-sea. These organisms contribute significantly to the total living biomass within these systems, serve as the major top–down control on bacterial assemblages, and are an important source of mortality for microalgae and other heterotrophic nanoflagellates. From many recent studies, it is generally accepted that HNF is one of the most important bacterial consumers. They also function as important remineralizers of organic matter and nutrients in aquatic systems. In accordance with these important ecological roles, heterotrophic nanoflagellates have been the subject of considerable study both in the field and laboratory.

Stable nitrogen and carbon isotopes in sediments and biota from three tropical marine food webs: Application to chemical bioaccumulation assessment

2017 ◽  
Vol 36 (9) ◽  
pp. 2521-2532 ◽  
Author(s):  
Hui Zhang ◽  
Yun Teng ◽  
Tra Thi Thanh Doan ◽  
Yun Wei Yat ◽  
Sheot Harn Chan ◽  
...  
Keyword(s):  
Food Webs ◽  
Carbon Isotopes ◽  
Marine Food Webs ◽  
Marine Food

scholarly journals Krill: a potential vector for domoic acid in marine food webs

2002 ◽  
Vol 237 ◽  
pp. 209-216 ◽  
Author(s):  
S Bargu ◽  
CL Powell ◽  
SL Coale ◽  
M Busman ◽  
GJ Doucette ◽  
...  
Keyword(s):  
Food Webs ◽  
Domoic Acid ◽  
Potential Vector ◽  
Marine Food Webs ◽  
Marine Food

Feeding habits and trophic level of the smooth hammerhead shark, Sphyrna zygaena (Carcharhiniformes: Sphyrnidae), off Ecuador

2018 ◽  
Vol 99 (3) ◽  
pp. 673-680 ◽  
Author(s):  
Colombo Estupiñán-Montaño ◽  
Luis Cedeño-Figueroa ◽  
José F. Estupiñán-Ortiz ◽  
Felipe Galván-Magaña ◽  
Alejandro Sandoval-Londoño ◽  
...  
Keyword(s):  
Trophic Level ◽  
Feeding Habits ◽  
Trophic Niche ◽  
Commercial Fishing ◽  
Dosidicus Gigas ◽  
Apex Predators ◽  
Marine Food Webs ◽  
Fishing Vessels ◽  
Marine Food ◽  
Index Of Relative Importance

As apex predators, sharks are known to play an important role in marine food webs. Detailed information on their diet and trophic level is however needed to make clear inferences about their role in the ecosystem. A total of 335 stomachs of smooth hammerhead sharks, Sphyrna zygaena, were obtained from commercial fishing vessels operating in the Ecuadorian Pacific between January and December 2004. A total of 53 prey items were found in the stomachs. According to the Index of Relative Importance (%IRI), cephalopods were the main prey (Dosidicus gigas, Sthenoteuthis oualaniensis, Ancistrocheirus lesueurii and Lolliguncula [Loliolopsis] diomedeae). Sphyrna zygaena was thus confirmed to be a teutophagous species. The estimated trophic level of S. zygaena was between 4.6 and 5.1 (mean ± SD: 4.7 ± 0.16; males: 4.7; females: 4.8). Levin's index (BA) was low (overall: 0.07; males: 0.08; females: 0.09), indicating a narrow trophic niche. We found that sharks <150 cm in total length consumed prey of coastal origin, whereas sharks ≥150 cm foraged in oceanic waters and near the continental shelf. The analyses indicate that S. zygaena is a specialized predator consuming mainly squids.

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