Trophic overlap between marine mammals and fisheries in subtropical waters in the western South Atlantic

2020 ◽  
Vol 639 ◽  
pp. 215-232 ◽  
Author(s):  
R Machado ◽  
LR de Oliveira ◽  
PH Ott ◽  
M Haimovici ◽  
LG Cardoso ◽  
...  
Keyword(s):  
Marine Mammals ◽  
Fishery Management ◽  
Bottlenose Dolphins ◽  
Trophic Relationships ◽  
Commercial Fishing ◽  
Southern Brazil ◽  
Apex Predators ◽  
Coastal Marine ◽  
Fur Seals ◽  
Trophic Overlap

Marine mammals and humans are apex predators and both may compete for fish in ecosystems under continuous fishing pressure. We assessed the degree of trophic overlap between prey species found in the diet of 5 marine mammals (39 specimens of sea lion Otaria flavescens, 61 fur seals Arctocephalus australis, 76 franciscana dolphins Pontoporia blainvillei, 25 bottlenose dolphins Tursiops truncatus and 28 Lahille’s bottlenose dolphins T. gephyreus) and the catches of the 6 main commercial fishing gears used in southern Brazil (coastal gillnets, oceanic gillnets, purse seine, demersal pair trawling, bottom [single] trawl and double-rig trawling) between 1993 and 2016. An adjusted general overlap index indicated an overall moderate to high overlap. Specific overlap analysis showed that O. flavescens and T. truncatus presented high trophic relationships with fisheries, followed by T. gephyreus. Smaller interactions were observed for A. australis and P. blainvillei, even though they also exploit commercial fishing resources. Coastal gillnet and pair bottom trawling are the fisheries that most target the fish species favoured by O. flavescens, T. gephyreus and T. truncatus. The information presented in this study on trophic interactions may assist decision making for both fishery management and conservation measures for these apex predators. Commercial fishing activities are a major threat to marine mammals both regionally and globally. Current levels of fishing or its intensification may lead to dramatic changes in the coastal marine food web, including additional threats to coastal marine mammal populations in southern Brazil.

scholarly journals An assessment of thermal-image acquisition with an unmanned aerial vehicle (UAV) for direct counts of coastal marine mammals ashore

2018 ◽  
Vol 6 (2) ◽  
pp. 100-108 ◽  
Author(s):  
Oliver Jordan Gooday ◽  
Nicholas Key ◽  
Sharyn Goldstien ◽  
Peyman Zawar-Reza
Keyword(s):  
New Zealand ◽  
Thermal Imaging ◽  
Marine Mammals ◽  
Forest Canopy ◽  
Infrared Camera ◽  
Canopy Cover ◽  
Future Research ◽  
Infrared Thermal Imaging ◽  
Coastal Marine ◽  
Fur Seals

We investigated the efficacy of infrared thermal imaging devices for detecting coastal marine mammals in forested coastal environments. Our objective was to determine whether pinnipeds could be detected through the forest canopy using thermal imagery. We used a UAV-mounted and a ground-mounted infrared camera to survey New Zealand fur seals (Arctocephalus forsteri) located in Ohau Stream and Point Kean coastal shrub forest on the east coast of New Zealand. These methods were compared to paired photographs and walk-through counts. Ground-mounted thermal images detected more seals than paired photographs during the cooler times of the day (morning and evening). In contrast, aerial thermal videos were successful in detecting fur seals in open areas, but were less successful in areas of high canopy cover (>80%). We discuss the advantages and limitations of thermal imaging for population sampling and provide some recommendations for future research.

Trophic relationships of albatrosses associated with squid and large-mesh drift-net fisheries in the North Pacific Ocean

1997 ◽  
Vol 75 (4) ◽  
pp. 549-562 ◽  
Author(s):  
Patrick Gould ◽  
Peggy Ostrom ◽  
William Walker
Keyword(s):  
Pacific Ocean ◽  
Trophic Level ◽  
North Pacific ◽  
Marine Mammals ◽  
North Pacific Ocean ◽  
Transitional Zone ◽  
Trophic Relationships ◽  
Commercial Fishing ◽  
The North ◽  
The North Pacific

The diets of Laysan (Diomedea immutabilis) and black-footed albatrosses (D. nigripes) killed in squid and large-mesh drift nets in the transitional zone of the North Pacific Ocean were investigated by examining the contents of the digestive tracts and determining δ13C and δ15N values in breast-muscle tissue. The results show that (i) the combined prey of the two species of albatross consists of over 46 species of marine organisms including coelenterates, arthropods, mollusks, fish, and marine mammals; (ii) both species supplement their traditional diets with food made available by commercial fishing operations (e.g., net-caught squid and offal); (iii) while obtained from drift nets, diets of nonbreeding Laysan and black-footed albatrosses are dominated by neon flying squid (Ommastrephes bartrami); (iv) in the absence of drift-net-related food, Laysan albatrosses feed most heavily on fish and black-footed albatrosses feed most heavily on squid; and (v) based on δ15N values, nonbreeding adult Laysan albatrosses from the transitional zone of the North Pacific Ocean and Laysan albatross nestlings fed by adults from Midway Island in the subtropical Pacific feed at one trophic level and one-third of a trophic level lower than black-footed albatrosses, respectively.

scholarly journals The isotopic niche of Atlantic, biting marine mammals and its relationship to skull morphology and body size

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Massimiliano Drago ◽  
Marco Signaroli ◽  
Meica Valdivia ◽  
Enrique M. González ◽  
Asunción Borrell ◽  
...  
Keyword(s):  
Body Size ◽  
Atlantic Ocean ◽  
Fisheries Management ◽  
Marine Mammals ◽  
Trophic Position ◽  
Sympatric Species ◽  
Isotopic Niche ◽  
Apex Predators ◽  
Skull Morphology ◽  
Ecosystem Based Fisheries Management

AbstractUnderstanding the trophic niches of marine apex predators is necessary to understand interactions between species and to achieve sustainable, ecosystem-based fisheries management. Here, we review the stable carbon and nitrogen isotope ratios for biting marine mammals inhabiting the Atlantic Ocean to test the hypothesis that the relative position of each species within the isospace is rather invariant and that common and predictable patterns of resource partitioning exists because of constrains imposed by body size and skull morphology. Furthermore, we analyze in detail two species-rich communities to test the hypotheses that marine mammals are gape limited and that trophic position increases with gape size. The isotopic niches of species were highly consistent across regions and the topology of the community within the isospace was well conserved across the Atlantic Ocean. Furthermore, pinnipeds exhibited a much lower diversity of isotopic niches than odontocetes. Results also revealed body size as a poor predictor of the isotopic niche, a modest role of skull morphology in determining it, no evidence of gape limitation and little overlap in the isotopic niche of sympatric species. The overall evidence suggests limited trophic flexibility for most species and low ecological redundancy, which should be considered for ecosystem-based fisheries management.

scholarly journals Natura 2000 sites and fisheries in German offshore waters

2008 ◽  
Vol 66 (1) ◽  
pp. 155-169 ◽  
Author(s):  
Søren Anker Pedersen ◽  
Heino Fock ◽  
Jochen Krause ◽  
Christian Pusch ◽  
Anne L. Sell ◽  
...  
Keyword(s):  
Marine Mammals ◽  
Fishery Management ◽  
Conservation Status ◽  
Natura 2000 ◽  
Management Measures ◽  
Favourable Conservation Status ◽  
Management Plans ◽  
Natura 2000 Site ◽  
Environmentally Sound ◽  
Fishing Impacts

Abstract Pedersen, S. A., Fock, H., Krause, J., Pusch, C., Sell, A. L., Böttcher, U., Rogers, S. I., Sköld, M., Skov, H., Podolska, M., Piet, G. J., and Rice, J. C. 2009. Natura 2000 sites and fisheries in German offshore waters.–ICES Journal of Marine Science, 66: 155–169. The principal objective of sites selected as part of Natura 2000 is to achieve or maintain a favourable conservation status of habitats and species named in the EU Birds and Habitats directives. In the German exclusive economic zone, the habitat types protected by this legislation are sandbanks and reefs; protected species include marine mammals, seabirds, and specific migratory fish species. The ICES project Environmentally Sound Fishery Management in Protected Areas (EMPAS) aims to answer two questions: (i) To what extent do specific fishing activities significantly threaten attainment of the conservation objectives of the Natura 2000 sites? (ii) What management measures would reduce these conflicts and how effective would they be at helping to ensure the favourable condition of these sites? Assessments of fishing impacts on Natura 2000 sites require basic data on the conservation status of individual habitats and species, as well as data for fine-scale distributions of ongoing fishing activities. This paper describes and discusses the process used by the EMPAS project in developing fishery-management plans for each Natura 2000 site in German offshore waters.

scholarly journals Diffusion modeling reveals effects of multiple release sites and human activity on a recolonizing apex predator

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Joseph M. Eisaguirre ◽  
Perry J. Williams ◽  
Xinyi Lu ◽  
Michelle L. Kissling ◽  
William S. Beatty ◽  
...  
Keyword(s):  
Human Activity ◽  
Residence Time ◽  
Prey Availability ◽  
Commercial Fishing ◽  
Apex Predators ◽  
Sea Otters ◽  
Southeast Alaska ◽  
Bayesian Hierarchical ◽  
Factors Influencing ◽  
Multiple Population

Abstract Background Reintroducing predators is a promising conservation tool to help remedy human-caused ecosystem changes. However, the growth and spread of a reintroduced population is a spatiotemporal process that is driven by a suite of factors, such as habitat change, human activity, and prey availability. Sea otters (Enhydra lutris) are apex predators of nearshore marine ecosystems that had declined nearly to extinction across much of their range by the early 20th century. In Southeast Alaska, which is comprised of a diverse matrix of nearshore habitat and managed areas, reintroduction of 413 individuals in the late 1960s initiated the growth and spread of a population that now exceeds 25,000. Methods Periodic aerial surveys in the region provide a time series of spatially-explicit data to investigate factors influencing this successful and ongoing recovery. We integrated an ecological diffusion model that accounted for spatially-variable motility and density-dependent population growth, as well as multiple population epicenters, into a Bayesian hierarchical framework to help understand the factors influencing the success of this recovery. Results Our results indicated that sea otters exhibited higher residence time as well as greater equilibrium abundance in Glacier Bay, a protected area, and in areas where there is limited or no commercial fishing. Asymptotic spread rates suggested sea otters colonized Southeast Alaska at rates of 1–8 km/yr with lower rates occurring in areas correlated with higher residence time, which primarily included areas near shore and closed to commercial fishing. Further, we found that the intrinsic growth rate of sea otters may be higher than previous estimates suggested. Conclusions This study shows how predator recolonization can occur from multiple population epicenters. Additionally, our results suggest spatial heterogeneity in the physical environment as well as human activity and management can influence recolonization processes, both in terms of movement (or motility) and density dependence.

scholarly journals The Protection of Animals During Warfare

AJIL Unbound ◽  
2017 ◽  
Vol 111 ◽  
pp. 272-276
Author(s):  
Jérôme de Hemptinne
Keyword(s):  
Marine Mammals ◽  
Bottlenose Dolphins ◽  
Rapid Rate ◽  
Human Beings ◽  
Armed Groups ◽  
Military Operations ◽  
Protected Species ◽  
California Sea Lions ◽  
Animal Products ◽  
Sea Lions

In times of war, the first instinct is to relieve the suffering of human beings. Environmental and animal interests are always pushed into the background. However, warfare strongly affects natural resources, including animals, which makes animal issues a matter of great concern. Certain species have been vanishing at a rapid rate because of wars, often with disastrous effects on the food chain and on the ecological balance. Indeed, belligerents rarely take into account the adverse consequences of their military operations on animals. They even take advantage of the chaotic circumstances of war in order to poach protected species and to engage in the trafficking of expensive animal products. While generating billions of dollars each year, such poaching and trafficking allows armed groups to grow and to reinforce their authority over disputed territory. States have also trained, and continue to train, certain animals—principally marine mammals such as bottlenose dolphins and California sea lions—to perform military tasks, like ship and harbor protection, or mine detection and clearance. Millions of horses, mules, donkeys, camels, dogs, and birds are obliged to serve on various fronts (transport, logistics, or communications) and become particularly vulnerable targets.

scholarly journals Evaluation of the current state of small pelagic fisheries in the Colombian Pacific: ensuring the sustainability of the resource and evaluating its response to climatic events

2013 ◽  
Vol 33 ◽  
pp. 63-68 ◽  
Author(s):  
L. A. Zapata ◽  
B. S. Beltrán-León ◽  
J. C. Herrera ◽  
P. Jiménez-Tello ◽  
L. M. Prieto ◽  
...  
Keyword(s):  
Marine Mammals ◽  
Commercial Fishing ◽  
Spawning Period ◽  
Thermal Anomalies ◽  
Current State ◽  
Management Measures ◽  
Canned Foods ◽  
Total Capture ◽  
Reproductive Processes ◽  
Eggs And Larvae

Abstract. Commercial fishing of small pelagic species in Colombia, mainly "carduma" (Cetengraulis mysticetus) and "plumuda" (Opisthonema spp.), has been recorded since 1970. Both are used to produce fish meal for aquaculture and poultry and for canned foods. These two species are filter feeders, and therefore support higher levels of the food chain (other fish, birds and marine mammals), and artisanal fishermen use them as bait. Between 2005 and 2010, 86.131 t have been captured (X = 14.355 t yr−1), and a strong reduction was noticed in 2009 (6.969 t). Carduma is considered a total spawning species. However, from 1997 to 2000 and from 2008 to date, atypical reproductive behavior of the species has been observed, including partition of the spawning period and the reduction of the volume of eggs and larvae released to the environment. Both situations are linked to thermal anomalies such as El Niño and La Niña events. Therefore, the process of assigning the global quota of extraction has been revised to take into account the reduction of total capture during the last years and the inconsistencies of the reproductive processes. The Ministry of Agriculture reduced the quota by 10%, leaving available a total of 27 000 t for 2010 and reduced it again to 25 000 t for 2011. It is important to maintain the management measures that are already implemented on this resource (bans during reproduction seasons, catch quotas, regulation of mesh sizes for the fishing nets, and limiting the number of new vessels) and considering other measures such as season closure for recruitment and establishment of marine protected areas to further contribute to the sustainability of these fisheries.

scholarly journals Cetacean Research and Citizen Science in Kenya

2021 ◽  
Vol 8 ◽  
Author(s):  
Michael Gilbert Mwango’mbe ◽  
Jane Spilsbury ◽  
Steve Trott ◽  
Judith Nyunja ◽  
Nina Wambiji ◽  
...  
Keyword(s):  
Citizen Science ◽  
Marine Mammal ◽  
Marine Mammals ◽  
Bottlenose Dolphins ◽  
Conservation Strategies ◽  
Science Data ◽  
Pilot Whale ◽  
Area Of Interest ◽  
Mammal Conservation ◽  
Kenyan Coast

In 2011, several non-governmental and government agencies established the Kenya Marine Mammal Network (KMMN) to provide a platform for the consistent collection of data on marine mammals along the Kenyan coast, identify areas of importance and engage marine users and the general public in marine mammal conservation. Prior to the KMMN, relatively little was known about marine mammals in Kenya, limiting conservation strategies. The KMMN collects data nationwide through dedicated surveys, opportunistic sightings and participative citizen science, currently involving more than 100 contributors. This paper reviews data on sightings and strandings for small cetaceans in Kenya collated by the KMMN. From 2011 to 2019, 792 records of 11 species of small cetaceans were documented. The most frequently reported inshore species were the Indo-Pacific bottlenose dolphin and Indian Ocean humpback dolphin. Offshore species, included killer whales, short-finned pilot whale and long-snouted spinner dolphin. Indo-Pacific bottlenose dolphins, long-snouted spinner dolphins, striped dolphins and Risso’s dolphins were recorded through stranding reports. The efforts of the KMMN were disseminated through international meetings (International Whaling Commission, World Marine Mammal Conference), national status reports, outreach and social media. Data has also supported the identification of three IUCN Important Marine Mammal Areas and one Area of Interest in Kenya. Further research is needed to improve estimates of cetacean abundance and distribution, particularly in unstudied coastal areas, and to assess the extent of anthropogenic threats associated with fisheries, coastal and port development, seismic exercises and unregulated tourism. The expansion of the network should benefit from the participation of remote coastal fishing communities, government research agencies, tourism and seismic operations, among others. The KMMN demonstrated the value of dedicated and citizen science data to enhance marine mammal conservation strategies to boost awareness and eco-tourism and to bring the public and science closer together, promoting research and effective conservation efforts.

scholarly journals Spatial and temporal variation in the occurrence of bottlenose dolphins in the Chesapeake Bay, USA, using citizen science sighting data

PLoS ONE ◽  
2021 ◽  
Vol 16 (5) ◽  
pp. e0251637
Author(s):  
Lauren Kelly Rodriguez ◽  
Amber D. Fandel ◽  
Benjamin R. Colbert ◽  
Jamie C. Testa ◽  
Helen Bailey
Keyword(s):  
Chesapeake Bay ◽  
Citizen Science ◽  
Marine Mammals ◽  
Generalized Additive Models ◽  
Bottlenose Dolphins ◽  
Temporal Distribution ◽  
Additive Models ◽  
Spatial And Temporal Variation ◽  
Estuarine System ◽  
Predictive Tool

Bottlenose dolphins (Tursiops truncatus) are migratory marine mammals that live in both open-ocean and coastal habitats. Although widely studied, little is known about their occurrence patterns in the highly urbanized estuary of the Chesapeake Bay, USA. The goal of this study was to establish the spatial and temporal distribution of bottlenose dolphins throughout this large estuarine system and use statistical modeling techniques to determine how their distribution relates to environmental factors. Three years (April-October 2017–2019) of dolphin sighting reports from a citizen-science database, Chesapeake DolphinWatch, were analyzed. The dolphins had a distinct temporal pattern, most commonly sighted during summer months, peaking in July. This pattern of observed occurrence was confirmed with systematic, passive acoustic detections of dolphin echolocation clicks from local hydrophones. Using spatially-exclusive Generalized Additive Models (GAM), dolphin presence was found to be significantly correlated to spring tidal phase, warm water temperature (24–30°C), and salinities ranging from 6–22 PPT. We were also able to use these GAMs to predict dolphin occurrence in the Bay. These predictions were statistically correlated to the actual number of dolphin sighting reported to Chesapeake DolphinWatch during that time. These models for dolphin presence can be implemented as a predictive tool for species occurrence and inform management of this protected species within the Chesapeake Bay.

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