Important Feeding Habitat Research Articles

Multi‐year monitoring shows higher species richness and diversity of fish assemblages in a Danish seagrass meadow as compared to neighbouring non‐vegetated areas

AbstractSeagrass meadows provide an important nursery and feeding habitat for fish, globally. However, limited data exist on how these vegetated coastal ecosystems affect local fish stocks over longer time periods. By means of beach seine hauling with a bio‐monitoring seine net, we collected fish data in Kronborg Bay (Denmark) over 4 years. The bay contains both vegetated and bare sediment areas in close proximity to Kronborg Castle in Elsinore and is part of the Øresund strait; a dynamic marine environment linking the Baltic Sea with the inner Danish waters (Kattegat). We investigated the biodiversity and fish abundance in a healthy seagrass meadow and compared it with a bare adjacent sediment area. We show that seagrass is important for fish species like the Atlantic cod, the two‐spotted goby, and the broadnosed pipefish. The seagrass meadow harboured more fish species and higher biodiversity, while the number of individuals was higher in the adjacent bare sediment area as a result of high abundances of lesser sand eel. Pilou's evenness and the Shannon‐Wiener index showed 2–4‐fold higher biodiversity in the seagrass meadow. The seagrass meadow harboured about 35% more fish species than the bare adjacent sediment. The Atlantic cod was almost entirely found in the seagrass meadow, while lesser sand eel that showed an overall increase in abundance in both habitats, represented the largest proportion of the total number of fish individuals (up to about 60%) and was mostly found on the bare adjacent sediment. Species abundance was analysed for changes over time, where, for example the European plaice showed an increase in abundance over the 4‐year period of investigation. Seagrass meadows can thus be very important for the Atlantic cod population in the Øresund strait and generally for local fish productivity, abundance and diversity.

Dam‐induced difference of fish habitat distribution in the fluctuating backwater zone of the Three Gorges Dam

AbstractChanges in fish habitat induced by dam construction in the downstream river have been well documented in an increasing body of literature. Fish habitats in the backwater zone of dams have undergone dramatic changes, which have still remained poorly understood. This study aims to provide a more complete understanding of fish habitat distribution and clarify fish habitat utilization patterns in the upstream dam in order to adopt effective remediation activities. This study was conducted in the Three Gorges Dam (TGD) as it is the world's largest installed capacity hydropower station, with a backwater zone length of about 660 km. Four major Chinese carp (FMCC) were selected as target fish species, and fish habitat distribution upstream of TGD was assessed by integrating the swimming ability and environmental preference of different fish species into their critical life stages. Assessment results at different life stages of the target fish species showed that June was a critical period for spawning activities FMCC in the fluctuating backwater zone of TGD. The riverbank was an important feeding habitat for FMCC, and the high‐velocity flow in the centre of the channel exceeded the limits of the swimming ability of target fish. The fish habitat distribution in the fluctuating backwater zone of TGD was heavily affected by runoff from April to September and by dam operation from October to March of the next year. This work provide valuable information about river conservation and management in the upstream of TGD.

The best watering hole in town: Characteristics of ponds used by an endangered bat in an urbanizing boreal landscape

Small waterbodies, or ‘ponds’, have an important role in maintaining biodiversity and ecosystem services, particularly where freshwater sources are limited, such as arid or some urban environments. However, studies that examine the use of ponds by terrestrial wildlife are limited. In the boreal forest, aquatic habitats are important drinking and feeding habitat for endangered little brown bats (Myotis lucifugus), and their relative value likely varies based on their characteristics, such as size, adjacent land cover type, anthropogenic disturbance, and proximity to other water bodies. We examined the characteristics of ponds used by little brown bats along an urban-rural gradient in Yukon, Canada. We used ultrasonic detectors to sample 99 ponds and generalized linear mixed models to determine whether ponds with certain characteristics received more bat activity than others. Ponds were important habitat for little brown bats, as 98% of the ponds we sampled were used. Bats selected ponds based on local rather than landscape level factors, and there was less bat activity at ponds surrounded by additional open water/wetland habitat, which was contrary to our prediction. Ponds that were surrounded by additional open water/wetland habitat may have been too exposed for bats at high latitudes, where nights are short and not completely dark. Isolated ponds that are darker, such as those surrounded by mature forest, may be particularly valuable for little brown bats at high latitudes that exhibit risk-sensitive foraging. We suggest that ponds of comparatively high value for endangered little brown bats be further identified and that these ponds be protected from development, draining, and degradation, and the surrounding mature forest remains intact. More broadly, recognition and conservation of ponds and their surroundings as key habitat for species of bats requires further attention. Understanding the characteristics of ponds selected by threatened bats can help inform conservation priorities and measures that ensure the aquatic habitats they require are maintained in developing landscapes.

Brown trout (Salmo trutta L. 1758) and Arctic charr [Salvelinus alpinus (L. 1758)] display different marine behaviour and feeding strategies in sympatry.

Brown trout (Salmo trutta L. 1758) and Arctic charr [Salvelinus alpinus (L. 1758)] tagged with acoustic transmitters migrated from fresh water to the sea mainly in May and June, but with large individual variation in migration timing. For S. trutta, large individuals (42-86 cm total length) migrated earlier in the season than small individuals (18-27 cm). For S. alpinus, no such pattern was found, likely because of the small size range of tagged fish (28-41 cm). S. trutta stayed longer at sea than S. alpinus (average 2 vs. 1 month). Early migrants of S. trutta stayed for a shorter period at sea than late migrants, whereas no such pattern was observed for S. alpinus. Large S. trutta moved quickly away from the river and spent average 3 days to reach a receiver line 20 km from the river mouth, whereas small S. trutta and S. alpinus migrating that far spent 2-3 weeks on the same distance. S. trutta utilized the entire fjord system and had a greater proportion of long-distance migrants (>20 km, 78% and 59% of large and small S. trutta, respectively) than S. alpinus (29%). S. alpinus mostly stayed in the inner fjord areas, and none were recorded in the outermost part of the fjord. The difference in the use of marine areas may be caused by variation in prey choice and spatial distribution of the preferred prey groups. Stable isotope analysis showed that S. trutta had been feeding at a higher trophic level than S. alpinus. S. trutta had mainly fed on marine fish and shrimps, whereas S. alpinus had large proportions of freshwater invertebrates in the diet, suggesting that the estuary with benthos and amphipods drifting from the river was an important feeding habitat for S. alpinus. In conclusion, major differences in habitat use, migration patterns and feeding strategies were found between sympatric anadromous S. trutta and S. alpinus while at sea.

Effects of changing temperature phenology on the abundance of a critically endangered baleen whale

Incorporating the effects of climate change in species management strategies is one of today’s greatest conservation challenges. Mechanistic models can be used to address these challenges because they explain how climate change effects cascade through ecosystems and influence species distributions. We used structural equation models to test hypotheses about the cascading effects of climate change and basin-scale variables on the local abundance of North Atlantic right whales, a critically endangered species, in a historically important feeding habitat. We found that effects of the North Atlantic Oscillation, a basin-scale variable, on local right whale abundance occurred through a cascade of effects on other ecosystem variables, including chlorophyll a concentration, Calanus finmarchicus abundance, and zooplankton patchiness. These effects varied by month. We also found that the western Gulf of Maine spring thermal transition date (a proxy for climate change) is a major direct and indirect driver of variations in local right whale abundance. The indirect effect of earlier spring transition dates, through a pathway of prey abundance, suggested a decrease in local right whale abundance. However, right whale abundance increased because of the direct effect of regional spring transition date. The direct effect suggests that right whales may be using regional temperatures as a movement cue. The counter-acting direct and indirect effects of spring transition date suggest that right whales could face a mismatch with their prey, which could ultimately result in another large-scale distribution shift. Our causal modeling approach demonstrates that the influence of climate change on local right whale abundance in the Gulf of Maine cascades through a network of variables. These cascading effects make predicting local right whale abundance challenging and suggest that successful endangered species conservation requires identifying the mechanisms underlying species distributions.

Large-scale historic habitat loss in estuaries and its implications for commercial and recreational fin fisheries

AbstractEstuaries provide important nursery and feeding habitat for numerous commercially and ecologically important fish, however, have been historically subject to substantial habitat alteration/degradation via environmental fluctuations, sea level rise, human activity on intertidal habitats, and adjacent land management. This review has summarized estuarine habitat use for 12 economically important finfish in the United Kingdom, of which seven were found to utilize estuarine habitats e.g. saltmarsh during their life cycle. This review reveals that ∼2500 km2 of intertidal habitat has been lost from estuaries in England and Wales since 1843. The implications of this large-scale habitat loss and continued anthropogenic disturbance within estuaries for a variety of fish species is discussed, in particular the requirement of finfish for particular habitats to be accessible and in a suitable condition. As a result of the high economic and social value of commercial and recreational fisheries, it is suggested that further research attention should investigate the spatial ecology of fish. Holistic fisheries management policies should also be considered, which would both sustainably manage fisheries landings but also account for the habitat requirements of the fisheries species.

Differences in dietary specialization, habitat use and susceptibility to human disturbance influence feeding rates and resource partitioning between two migratory Numenius curlew species

Migratory shorebirds select stopover sites to fuel their migration across heterogeneous coastal landscapes with abundant prey resources. Quantifying the degree of dietary specialization between closely-related species and how they partition resources across different coastal habitat types during both spring and autumn migration could identify some interesting possibilities for conservation management given the extent of anthropogenic habitat degradation at critical stopover sites. Here we used a comparative approach to examine diet specialization and feeding rates of two migratory Numenius curlew species, Far Eastern Curlew Numenius madagascariensis and Eurasian Curlew N. arquata populations, at an important stopover site in the Yellow Sea, China, and to assess the influence of habitat type, presence of human disturbance (activities related to aquaculture and oil production), and migratory season on their feeding behavior. Far Eastern Curlews were more dependent on tidal crabs and exhibited less dietary flexibility than its closely-related congener. Feeding rates on crabs by Far Eastern Curlews were not significantly different between mudflat and Suaeda salsa saltmarsh habitat but were negatively influenced by human disturbance and were higher during spring migration. In contrast, these effects were not apparent for Eurasian Curlew which fed predominantly on ragworms in saltmarsh habitat. The differences in prey type and feeding rates between adjacent habitats and migration seasons could explain how these two congeners fit syntopically along coastal wetland resource gradients. The extensive utilization of S. salsa habitat by both species suggests that saltmarshes represent an important feeding habitat for these species and that further conservation efforts aimed at reducing human disturbance would benefit both species and may lead to improved feeding rates for Far Eastern Curlews.

Wayuú capture of green turtles, Chelonia mydas, in the Gulf of Venezuela: A major Caribbean artisanal turtle fishery

Fisheries, either directed or via bycatch, are a major cause of decline in global populations of marine turtles. Although artisanal fisheries are often seen as lower-impact than industrial fisheries, they may be among the most serious threats to green turtles. Between 2005 and 2008, to better understand the impacts of such fisheries in the High Extraction Zone of the Gulf of Venezuela (HEZ-GV), an important feeding habitat for green turtles, we interviewed fishers, observed fishing activities directly, and counted, measured, and marked discarded turtle carapaces at fishing ports and traditional markets. From these, we estimated that at least 3,402 ± 247 turtles/year were extracted with artisanal nets, suggesting that the HEZ-GV artisanal turtle fishery may have been among the most active in the Caribbean at the time, with a CPUE of 0.04 turtles/km-net*hour ±0.014. However, capture was not selective, confirming prior anecdotal information suggesting that this fishery supplies mainly subsistence and not commercial use. Harvested turtles consisted mainly of juveniles (64%, CCLmin = 55.7 cm ± SE 0.9), and subadults (35%, CCLmin = 78.9 cm ± 0.6 cm), with very few adults (1%, CCLmin = 98 cm ± 0.6 cm). Our findings highlight the need for continued monitoring of the artisanal turtle fishery in the HEZ-GV, particularly given the possibility of increased reliance on aquatic bushmeat sources in Venezuela's present socio-economic crisis. More broadly, they also indicate that scientifically based catch guidelines for marine turtles may be just as important in artisanal as in commercial fisheries, to ensure sustainability and mitigate harvest impacts.

Characterization of the feeding behavior of the green turtle (Chelonia mydas) in the Juréia-Itatins Mosaic's Conservation Units, South Coast of the São Paulo state

The Chelonia mydas occurs most frequently in the Cananeia-Iguape-Peruibe Environmental Protection Area and Conservation Units Jureia-Itatins, using coastal regions of the continent and islands of the region as a feeding area. It presents a habitat change during its ontogenetic development. The individuals migrate from the pelagic environment, in this stage they had an omnivorous diet, when they change this feeding area, to the neritic environment, they can have predominantly herbivorous´ diet. However, recent studies have suggested that both habitats change and, consequently, the diet changes may be optional. The objective of this study was to characterize the feeding behavior of green turtles in the municipality of Peruibe, south coast of Sao Paulo. The data were collected from October/2018 to October/2019, with the monitoring of the beaches and the study of the specimens found. This study was approved by the Ethics Committee on The Use of Animals (CEUA/IBIMM) n°. 008/18 and by the Biodiversity Authorization and Information System (SISBIO/ICMBio/MMA) n°. 50132. In the period, 7 individuals were collected who were submitted to biometrics, necropsy and food content collection to verify their composition. Organic and inorganic constituents were separated and the macroalgae found in the esophagus and stomach samples were submitted to a second screening, using morphology and staining as criteria. The mass frequency of each phylum of macroalgae was calculated. The results showed that the individuals were juveniles with CCL 36.33 cm and presented predominantly herbivore feeding behavior, because there was no food from animal origin, consisting only of shell fragments of molluscs and exoskeletons of crustaceans, whose intake may have been accidental. The total survey of macroalgae present in the esophagus and stomach were Chlorophyta (42.76%), Rhodophyta (33.19%) and Heterokontophyta (24.05%), the presence of diatoms was observed complementing the diet of the animals. In addition, it was found that all had anthropogenic residues in their gastrointestinal tracts, and 73.33% of total constituents found are associated with plastic and plastic bags from fishing activities. It was concluded that the Region of Peruibe is an important feeding and development habitat for the species. A problem related to solid waste pollution was observed which consequently shows the need to develop environmental education work with fishers, population and tourists oriented to recycling and the reduction of anthropogenic actions on site.

Underwater Ambient Noise in a Baleen Whale Migratory Habitat Off the Azores

Assessment of underwater noise is of particular interest given the increase in noise-generating human activities and the potential negative effects on marine mammals which depend on sound for many vital processes. The Azores archipelago is an important migratory and feeding habitat for blue (Balaenoptera musculus), fin (Balaenoptera physalus) and sei whales (Balaenoptera borealis) en route to summering grounds in northern Atlantic waters. High levels of low frequency noise in this area could displace whales or interfere with foraging behavior, impacting energy intake during a critical stage of their annual cycle. In this study, bottom-mounted Ecological Acoustic Recorders were deployed at three Azorean seamounts (Condor, Acores and Gigante) to measure temporal variations in background noise levels and ship noise in the 18-1,000 Hz frequency band, used by baleen whales to emit and receive sounds. Monthly average noise levels ranged from 90.3 dB re 1 μPa (Acores seamount) to 103.1 dB re 1 μPa (Condor seamount) and local ship noise was present up to 13% of the recording time in Condor. At this location, average contribution of local boat noise to background noise levels is almost 10 dB higher than wind contribution, which might temporally affect detection ranges for baleen whale calls and difficult communication at long ranges. Given the low time percentatge with noise levels above 120 dB re 1μPa found here (3.3 % at Condor), we woud expect limited behavioural responses to ships from baleen whales. Sound pressure levels measured in the Azores are lower than those reported for the Mediterranean basin and the Strait of Gibraltar. However, the currently unknown effects of baleen whale vocalization masking and the increasing presence of boats at the monitored sites underline the need for continuous monitoring to understand any long-term impacts on whales.

Seasonal home range shifts of the Siberian taimen (Hucho taimenPallas 1773): Evidence from passive acoustic telemetry in the Onon River and Balj tributary (Amur River basin, Mongolia)

Hucho taimen, the world's largest salmonid, is a potadromous species that is listed as endangered in Mongolia. While mature individuals are known to have extended longitudinal movements of over 90 km along main river channels, details of the seasonal movements and residency of individuals within and between tributary habitats have been largely undocumented. Therefore, the current research aimed to detect and quantify the seasonal distances moved by adult taimen (65–96 cm; n = 10) within and between the Onon River (Amur River basin) and a major tributary (Balj) over 12 months using passive acoustic telemetry. The median distance moved by taimen in spring was 17.4 km (n = 6), in summer 9.1 km (n = 4), autumn 4.7 km (n = 9) and winter 0.4 km (n = 8). However, there were no statically significant differences amongst these median seasonal home range sizes. Two taimen traversed between the Onon River and the Balj tributary during the study period, recording overall home ranges of 44.5 km and 126.1 km. One of these individuals moved twice, exiting the tributary in autumn and returning again in spring where it remained for 36 days, while the second taimen moved only once into the tributary in spring and re-entered the main channel in late summer after 85 days. Another two taimen entered surrounding smaller tributaries and recorded home ranges of 26.1 km and 29.2 km, while all remaining individuals were detected moving only within the waterway where they were originally captured and released (0.8–20.1 km). Taimen movements within tributaries such as the Balj can be extensive (<60 km), as they provide access to important spawning, feeding and overwintering habitats as well as refuge from adverse thermal and hydrological conditions. Thus to enhance population recovery, it is essential that current and future management and conservation efforts include preserving or restoring the ecological integrity and hydrological connectivity of these critical tributaries and the main river channel throughout the Onon and Amur River basins and across the remaining distribution of this endangered species.

Genetic structure and diversity of green sea turtle (Chelonia mydas) from South China Sea inferred by mtDNA control region sequence

We analyzed 88 control region sequences of green sea turtle (Chelonia mydas) from around Hainan Island in the South China Sea. These sequences had a length of 489 bp and revealed 8 mtDNA haplotypes of which four haplotypes (CMC1, CMC4, CMC7, and CMC8) had not been discovered before. Haplotype diversity (h) and nucleotide diversity (π) were 0.45 ± 0.054 and 0.0035 ± 0.0014, respectively. Neighbor-Joining tree based on control region sequences revealed that genetic relationship between green sea turtles from the South China Sea and from Japan Sea were very close. Clustering relationship based on control region sequences indicated that the South China Sea is an important breeding site and feeding habitat for green sea turtles, which connects with the Middle East Pacific, the Southwest Pacific and the Indian Ocean.

Habitat use of bonobos (Pan paniscus) at Wamba: Selection of vegetation types for ranging, feeding, and night-sleeping.

Understanding the habitat requirements of great apes is essential for effective conservation strategies. We examined annual habitat use of a bonobo group in the Wamba field site within the Luo Scientific Reserve, Democratic Republic of the Congo. Using satellite imagery, we categorized the group's ranging area into three forest types: (1) primary and old secondary forest (P/OS), (2) young secondary forest and agriculture (YS/Ag), and (3) swamp forest (Sw). We tracked the group for 1 year (2007-2008) and compared usage of the three forest types for ranging, feeding, and night-sleeping. We also recorded what the bonobos ate and monitored monthly fruit availability in each forest type. The group ranged and fed more often in P/OS and less often in YS/Ag and Sw than expected based on habitat availability. Also, the group slept mostly in P/OS (94% of nights monitored), but also in YS/Ag (1%), and Sw (5%). Fruit availability in P/OS had no significant effect on habitat selection, but the group fed in YS/Ag most often during the two months when fruits in P/OS were least abundant. In June, when fruit of Uapaca spp. (selectively eaten by bonobos) was generally abundant in Sw, the group mostly ranged and slept there. The bonobos fed most often on herbaceous plants in all three forest types. In Sw, the bonobos frequently ate mushrooms. Our results show that semi-open forest with abundant herbaceous plants such as YS/Ag could be an important feeding habitat and may provide fallback food for bonobos when fruits are scarce. Furthermore, Sw can serve seasonally as a main habitat to complement P/OS if adequate food resources and tree nesting opportunities are available. We conclude that bonobos use diverse habitats depending on their needs and we highlight the importance of minor-use habitats for sustaining populations of target species in conservation planning.

Urbanisation alters processing of marine carrion on sandy beaches

Sandy shores are highly attractive for urban development. Urbanisation of beaches is, however, not without environmental consequences, but metrics of ecological change along metropolitan coasts are poorly developed. This lack of metrics impedes environmentally effective coastal zone management. Here we test the effects of urbanisation on a pivotal ecological process on sandy shorelines: carrion removal by vertebrate scavengers. Scavenging is a key process linking ocean and land ecosystems via animal carcasses deposited on beaches and subsequently consumed by mostly terrestrial animals. In this study, experimentally placed fish carcasses were monitored with motion-triggered cameras on urban and rural beaches on the east coast of Australia. Urbanisation substantially influenced the structure of the scavenger guild and the frequency of carrion removal within 24h. Large raptors were abundant on rural beaches where they rapidly detected and consumed carrion (98% of carcasses removed within 24h). We detected no scavenging activity of raptors on urban beaches, where scavenging birds of prey were functionally replaced by nocturnally foraging, non-native mammals (red fox, Vulpes vulpes) or feral species (cats, dogs) known to threaten beach-dwelling wildlife. Our findings emphasise the value of non-urbanised coastal dunes and sandy beaches as important feeding sites and habitats for iconic and threatened raptors. We also show that human changes in coastal land-use profoundly alter ecological structures and processes on sandy shorelines, aspects that warrant explicit inclusion in landscape management and planning of the coastal strip.

On the drivers of phytoplankton blooms in the Antarctic marginal ice zone: A modeling approach

AbstractThe pelagic province of the Southern Ocean generally has low levels of primary production attributable to a short growing season in the higher latitudes, a deep mixed layer, and iron limitation. Exceptions include phytoplankton blooms in the marginal ice zone (MIZ) during spring and summer sea‐ice retreat. The prevailing hypothesis as to the drivers of the blooms is that sea‐ice retreat increases the vertical stability of the water column through the production of melt water and provides shelter from wind mixing in areas of partial sea‐ice coverage. These conditions are favorable to phytoplankton growth by allowing them to maintain their position in the upper reaches of the water column. This work investigates the drivers of MIZ blooms using a biochemically coupled global circulation model. Results support the hypothesis in that physical conditions related to a shallow, vertically stable water column (e.g., mixed layer depth and available light) were the most significant predictors of bloom dynamics, while nutrient limitation was of lesser importance. We estimate that MIZ blooms account for 15% of yearly net primary production in the Southern Ocean and that the earlier phases of the MIZ bloom, occurring under partial ice coverage and invisible to remote sensing, account for about two thirds of this production. MIZ blooms were not found to enhance depth‐integrated net primary production when compared to similar ecological provinces outside of the MIZ, although the elevated phytoplankton concentrations in surface waters are hypothesized to provide important feeding habitats for grazing organisms such as krill.

Disproportionate importance of nearshore habitat for the food web of a deep oligotrophic lake

In large deep oligotrophic lakes, multiple lines of evidence suggest that the shallow nearshore water provides disproportionately important feeding and breeding habitat for the whole-lake food web. We examined the trophic importance of the nearshore environment, human impacts nearshore, and several approaches to disturbance detection in a deep (190 m) oligotrophic lake with relatively modest residential development. In Lake Crescent, on the Olympic Peninsula of Washington (USA), stable isotope analysis demonstrated that apex salmonid predators derived more than 50% of their carbon from nearshore waters, even though this nearshore water accounted for only 2.5% of total lake volume. Unfortunately, it is this land–water interface that is initially degraded as shorelines are developed. We hypothesised that under these conditions of relatively modest disturbance, the effects of residential development would be strongly localised near to shore. Indeed, we found striking differences between developed and undeveloped sites in periphyton and associated organic matter, though there were no offshore signals of human impact in water nutrient analysis or paleolimnological investigations. Together, these results suggest that nearshore biological monitoring should be integrated in lake management plans to provide ‘early warning’ of potential food-web repercussions before pollution problems are evident in open water and comparatively intractable.

Health Indices of the Green Turtle (Chelonia mydas) Along the Pacific Coast of Baja California Sur, Mexico. I. Blood Biochemistry Values

Abstract The green sea turtle (also known locally as black turtle; Chelonia mydas) is 1 of 5 species of sea turtles found along the coast of the state of Baja California Sur, Mexico, where several bays and lagoon systems provide an important growth and feeding habitat. We characterized blood biochemistry values of 67 green turtles captured at 2 mangrove estuaries along the Pacific coast of the Baja California Peninsula, Mexico, from 2005 to 2007. Blood samples were collected from live turtles for biochemical analysis of 18 parameters and analyzed by physical state (healthy, injured), size classes, season, and geographic location. Green turtles showed differences in the variability of the biochemical parameters between the 2 sites. In Punta Abreojos, injured sea turtles had lower calcium (28%), potassium (28%), and inorganic phosphorus (34.5%) levels and higher cholinesterase activity (16%) compared to healthy turtles. Juvenile turtles collected in Bahia Magdalena had higher glucose levels (34%) than subad...

Spring distribution and density of minke whale Balaenoptera acutorostrata along an offshore bank in the central North Sea

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 408:265-274 (2010) - DOI: https://doi.org/10.3354/meps08598 Spring distribution and density of minke whale Balaenoptera acutorostrata along an offshore bank in the central North Sea Marijke N. de Boer* Wageningen IMARES, Institute for Marine Resources and Ecosystem Studies, Postbus 167, 1790 AD Den Burg, The Netherlands *Email: seven.seasmc@yahoo.co.uk ABSTRACT: Minke whales were recorded in the central North Sea in an area characterised by frontal features and high productivity northeast of the Dogger Bank (4677 km2). Survey efforts were carried out from 28 March to 2 July 2007, at a finer scale than in earlier studies in the region, using 2 vessels as platforms of opportunity and a dedicated line-transect survey vessel following distance sampling methods. The high density of whales indicated that this offshore bank slope is an important spring habitat for minke whales in the North Sea. In total, 77 sightings of minke whales comprising 130 individuals were recorded. The peak density of minke whales was estimated to be 0.029 whales km–2 (minimum estimate, 95% CI: 0.012 to 0.070) in May. During peak abundance, the minke whales temporarily congregated in the area, suggesting that the whales were taking advantage of the local spring abundance of sandeels. The density found was higher than previous studies have suggested for the central North Sea. The results correspond to recent observations of minke whale redistribution within the North Sea, and these may be related to a decline in sandeel availability elsewhere in the North Sea. Offshore banks that aggregate prey may therefore become increasingly important feeding habitats for minke whales and other top predators in the North Sea. The observed habitat preference of minke whales along this offshore bank appeared to be similar to that observed in coastal areas, and this suggests some degree of generality regarding the preference for this type of habitat. KEY WORDS: Minke whale · Distribution · Density · Relative abundance · Offshore bank · Platform of opportunity · Line-transect survey · Central North Sea Full text in pdf format PreviousNextCite this article as: de Boer MN (2010) Spring distribution and density of minke whale Balaenoptera acutorostrata along an offshore bank in the central North Sea. Mar Ecol Prog Ser 408:265-274. https://doi.org/10.3354/meps08598 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 408. Online publication date: June 03, 2010 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2010 Inter-Research.

Feeding activity of cattle egrets and intermediate egrets at different stages of rice culture in Korea

This study was conducted to investigate the feeding efficiency of the cattle egret (Bubulcus ibis) and the intermediate egret (Ardea intermedia) in relation to the stage of rice culture during two breeding seasons, 2006 and 2007, in Asan city, Chungcheongnam-do, South Korea. Cattle egrets caught mainly small invertebrate prey (insects and spiders, 98.4%) during all stages of rice cultivation, and had a higher prey capture rate in the plowing stage (14.98 prey/min) than in other stages (2.82-3.51 prey/min). Therefore, the biomass intake rate of cattle egrets was highest in the plowing stage. The intermediate egret captured both loaches (43.4%) and small invertebrates (50.6%). The prey capture rates of intermediate egrets increased gradually from the flooding stage (0.38 prey/min) to the planting stage (1.09 prey/min), and decreased in the growing stage (1.04 prey/min). However, intermediate egrets had the highest biomass intake rates in the plowing stage because more loaches were caught in the plowing stage (0.54 loaches/min) than other stages (0.23-0.36 loaches/min). Consequently, both intermediate egrets and cattle egrets had high energy intakes in the plowing stage and rice fields provided an important feeding habitat for both species.

Importance of different carbon sources for macroinvertebrates and fishes of an interlinked mangrove–mudflat ecosystem (Tanzania)

Mangroves function as important shelter and feeding habitats for marine fauna, but the degree to which mangrove-derived carbon contributes to local food webs has long been debated. In this study, stable isotope analysis was used as a technique to elucidate the role of mangrove carbon in the diets of the macroinvertebrate and fish fauna of an intertidal fringing mangrove forest and adjacent intertidal/subtidal mudflats in a macrotidal Tanzanian estuary. The expectation was that sessile species and those with low motility depend to a larger extent on local carbon sources than highly motile species. A clear distinction in δ 13C was present between primary producers from mangrove and mudflat habitats. Macroinvertebrates revealed a gradient in their δ 13C where Sesarma crabs were the only species that directly utilised mangrove carbon by feeding on mangrove leaves/detritus. Uca crabs and the gastropod Littoraria scabra showed a higher dependence on microphytobenthos from the mangrove substratum. Among the fish fauna, the amphibious mudskipper was the only species to which the mangroves were accessible during low tide. Consequently this was the only fish species for which it was clear that it fed in the mangrove habitat, most commonly on mangrove-associated Uca crabs. All other species of sessile as well as motile macroinvertebrates and fish from the mangrove and mudflat habitat showed a high degree of utilisation of mudflat carbon. Overall, mangrove carbon thus contributed little to the mangrove and mudflat food webs, despite the high tidal amplitude and the resulting potential for exchange of carbon and fauna in the estuary studied here. Utilisation of mangrove carbon appears to depend more on the ecology of the species in consideration (e.g., species-specific use of zones within the mangrove habitat) than on their potential motility or tolerance to exposure during low tide.