Age Area Research Articles

Integrated system for organizing effective biotechnical protection of siberian roe deer (capreolus pygargus) in a specially protected natural area

To preserve the Siberian roe deer, the most vulnerable species of the deer family, in conditions of high snow conditions, integrated methods of its biotechnical protection are necessary. The involvement of fallow lands in the biotechnical crop rotation, the creation of large forage areas is the basic basis for the conservation of this biological species in the anomalously critical periods of the winter cycle.

ANÁLISIS SOCIOECONÓMICO PARA IDENTIFICAR OPORTUNIDADES DE DESARROLLO DE LA GANADERÍA DOBLE PROPÓSITO EN TROPICO SECO

<p><strong>Background.</strong> The dual-purpose production system is a major economic activity in rural areas due to the income generated from milk and meat sales. <strong>Objective</strong>. The aim was to conduct an economic analysis of three groups of dual-purpose production units.<strong> Methodology</strong>. The groups w: i. MIDP; with greater orientation to milk production; ii. TDP or traditional dual purpose and iii. MEDP that only produce meat. The information was obtained during 2015 by technical-economic assessment of 67 farms in the central highlands of Mexico. The partial budget methodology, and variance analysis (P<0.05) for economic and management indicators with normal distribution and Kruscal Wallis test (P<0.05) on the variables without normal distribution or expressed as a percentage were used. Also, a Student's t test was performed for the variables related to milk production only for MIDP and TDP groups. <strong>Results.</strong> Differences (P<0.05) between groups were observed in the labor available and agricultural area, values that were greater in MIDP, as well as the forage area in meat DP group. It was observed that MIDP are PU of recent creation, medium size (24.50 ± 5.72 cows) and contract labor; the TDP are old PU with older farmers and medium size to (26.1 3.70 ± 3.70 cows) and, meat DP group are old and small PU (15.20 ± 2.52 cows), with young farmers and family labor. Equally differences (P<0.05) between groups were observed in the total net margin for milk and cattle sales and in the unit net margin (ha and cow). In both cases, profits were greater in MIDP. <strong>Implications. </strong>The work contributed to the understanding of the dual-purpose livestock guidelines and their development based on the productive orientation<strong>. Conclusion.</strong> It concluded that milk production generates greatest economic profit and the activity it postulated as a development alternative, although number of PU is small and the traditional dual-purpose system is maintained in a stable economy activity. In counterpart, the meat production system presents greater economic instability and less development for the lowest profit margins.</p>

Intrapopulation foraging niche variation between phenotypes and genotypes of Spirit bear populations.

Foraging niche variation within a species can contribute to the maintenance of phenotypic diversity. The multiniche model posits that phenotypes occupying different niches can contribute to the maintenance of balanced polymorphisms. Using coastal populations of black bears (Ursus americanus kermodei) from British Columbia, Canada, we examined potential foraging niche divergence between phenotypes (black and white “Spirit” coat color) and between genotypes (black‐coated homozygote and heterozygous). We applied the Bayesian multivariate models, with biotracers of diet (δ13C and δ15N) together comprising the response variable, to draw inference about foraging niche variation. Variance–covariance matrices from multivariate linear mixed‐effect models were visualized as the Bayesian standard ellipses in δ13C and δ15N isotopic space to assess potential seasonal and annual niche variation between phenotypes and genotypes. We did not detect a difference in annual isotopic foraging niche area in comparisons between genotypes or phenotypes. Consistent with previous field experimental and isotopic analyses, however, we found that white phenotype Spirit bears were modestly more enriched in δ15N during the fall foraging season, though with our modest sample sizes these results were not significant. Although also not statistically significant, variation in isotopic niches between genotypes revealed that heterozygotes were moderately more enriched in δ13C along hair segments grown during fall foraging compared with black‐coated homozygotes. To the extent to which the pattern of elevated δ15N and δ13C may signal the consumption of salmon (Oncorhynchus spp.), as well as the influence of salmon consumption on reproductive fitness, these results suggest that black‐coated heterozygotes could have a minor selective advantage in the fall compared with black‐coated homozygotes. More broadly, our multivariate approach, coupled with knowledge of genetic variation underlying a polymorphic trait, provides new insight into the potential role of a multiniche mechanism in maintaining this rare morph of conservation priority in Canada's Great Bear Rainforest and could offer new understanding into polymorphisms in other systems.

Foraging in marine habitats increases mercury concentrations in a generalist seabird

Methylmercury concentrations vary widely across geographic space and among habitat types, with marine and aquatic-feeding organisms typically exhibiting higher mercury concentrations than terrestrial-feeding organisms. However, there are few model organisms to directly compare mercury concentrations as a result of foraging in marine, estuarine, or terrestrial food webs. The ecological impacts of differential foraging may be especially important for generalist species that exhibit high plasticity in foraging habitats, locations, or diet. Here, we investigate whether foraging habitat, sex, or fidelity to a foraging area impact blood mercury concentrations in western gulls (Larus occidentalis) from three colonies on the US west coast. Cluster analyses showed that nearly 70% of western gulls foraged primarily in ocean or coastal habitats, whereas the remaining gulls foraged in terrestrial and freshwater habitats. Gulls that foraged in ocean or coastal habitats for half or more of their foraging locations had 55% higher mercury concentrations than gulls that forage in freshwater and terrestrial habitats. Ocean-foraging gulls also had lower fidelity to a specific foraging area than freshwater and terrestrial-foraging gulls, but fidelity and sex were unrelated to gull blood mercury concentrations in all models. These findings support existing research that has described elevated mercury levels in species using aquatic habitats. Our analyses also demonstrate that gulls can be used to detect differences in contaminant exposure over broad geographic scales and across coarse habitat types, a factor that may influence gull health and persistence of other populations that forage across the land-sea gradient.

Multi-scale habitat selection and spatial analysis reveals a mismatch between the wintering distribution of a threatened population of Taiga Bean Geese Anser fabalis and its protected area

ABSTRACT Capsule Our multi-scale habitat selection and spatial analysis of a threatened population of Taiga Bean Geese Anser fabalis highlights the importance of monitoring and review programmes to determine whether species conservation measures are being implemented at the correct spatio-temporal scales. Aims To undertake a habitat selection and spatial analysis of an internationally important population of Taiga Bean Geese, and quantify the extent to which their foraging range overlaps with a protected area classified to protect their roost sites and foraging areas. Methods A five-year field count dataset was used to quantify foraging habitat selection at the population range scale. In addition, global positioning system (GPS)/ultra high frequency loggers were attached to 12 birds and GPS location data were collected to quantify foraging habitat selection at an individual foraging range scale. Results Generalized linear models predicted that, at the population foraging range scale, Taiga Bean Geese selected agriculturally improved pasture, and this selection was more pronounced at greater distances from public roads. At an individual foraging range scale, compositional analysis revealed that agriculturally improved pasture was significantly selected over all other habitats. There was a substantial mismatch between their individual foraging ranges and the protected area, with less than 35% (median: 21%; range 9.5–31.9%) of their individual full foraging ranges overlapping with the protected area. Discussion Fixed protected areas may fail to fully accommodate the spatio-temporal foraging dynamics of geese, however a more appropriate conservation measure may be the use of flexible management schemes to maintain their foraging areas within and beyond protected area boundaries. This case study highlights the importance of developing dynamic conservation strategies for species liable to undergo range shifts.

Response of grizzly bears (Ursus arctos) to pipelines in Alberta.

This research provides the first in-depth analysis of fine-scale grizzly bear habitat selection and movement patterns in response to the linear footprints cleared for below-ground pipelines in Alberta. Using an extensive set of GPS location data from collared grizzly bears, we were able to determine that grizzly bears selected for younger pipelines (mean age since last construction~6.5 years), which are known to have a greater abundance of important bear foods. Bears also selected for wider corridors that were disturbed for construction more than once. During the spring season, sex/age class was an important predictor of grizzly bear use of pipelines, with adult female bears more likely to use these features than other sex/age classes. Examination of movement patterns revealed that pipeline density influenced grizzly bears' movement rates and path straightness, particularly in the spring, when bears moved more slowly and movement paths were more tortuous in areas with higher pipeline densities. These movement patterns are consistent with foraging behavior and further indicate that bears are not exhibiting avoidance behaviors or displacement by pipeline features, and pipelines may be functioning as seasonally important foraging areas for grizzly bears in Alberta.

Foraging Behavior of Bottlenose Dolphins in the Shannon Estuary, Ireland as Determined through Static Acoustic Monitoring

The Shannon Estuary in Ireland is home to a resident population of bottlenose dolphins (Tursiops truncatus) and is designated as a Special Area of Conservation under the EU Habitats Directive. It is an important industrial area, with numerous deep-water berths for shipping. Despite its high conservation value, there are few published studies on habitat use or foraging behavior of the Shannon dolphins throughout the year. The present study assessed the year-round presence and foraging activity of bottlenose dolphins at different locations in the middle and inner estuary using static acoustic monitoring. Dolphin presence was found to decrease with increased distance from the estuary mouth, i.e., where the estuary meets the Atlantic Ocean, while at the same time, foraging was found to be considerably higher in the upriver areas, suggesting the inner estuary was an important foraging area. Model predictions for seasonal, tidal and diel foraging were highly variable across locations, indicating that changes in dolphin behavior occurred over relatively small geographical scales. These results indicate that conservation efforts should consider the Shannon Estuary as a dynamic aggregation of habitats and future development initiatives should attempt to mitigate disturbance to the dolphins during important foraging periods on seasonal and diel scales.

Variações microclimáticas e edáficas em sistemas silvipastoris no município de Belterra, Pará

The objective of this work was to evaluate microclimatic and edaphic variations in silvopastoral systems, a system in which forest, forage species and animals that graze in consortium are integrated for production. The research was conducted at Fazenda Boa Safra located in the municipality of Belterra. The data were collected in a timely manner in October 2016 in two environments: four forage areas and four arboreal areas with the species: Andiroba (Carapa guianensis Aubl), African Mahogany (Khaya ivorensis A. Chev.), Teak (Tectona grandis L. f.) and Cumaru (Dipteryx odorata Willd.). The variables studied were temperature, soil moisture, litter stock and canopy cover. The results indicate that coumaru is the species that offers better thermal comfort compared to other species, while andiroba stood out in the best litter supply. The role of vegetation cover promoted by trees in the silvopastoral system is highlighted, promoting a better surface temperature of the soil (2 cm deep) in relation to pasture.

Coastal foraging on the West Coast of South Africa in the midst of mid-Holocene climate change

The mid-Holocene (ca. 8200–4200 cal BP) brought about important climatic changes and environmental shifts to land and coastal systems, globally. Many of the human groups existing at that time were affected in various degrees by such important modifications to their foraging areas, including shorelines. Higher sea-levels (+1–3 m) were a prominent factor reshaping coastal landscapes and thus affecting coastal foraging in one or more ways. Hot and dry weather and relatively higher sea levels along the central west coast of South Africa impacted substantially on local coastal hunter-gatherer groups. These challenges were thought once to have been unsurmountable because of an apparent absence of sites dated to this period. Recently dated mid-Holocene assemblages allow us to gain insight into coastal resource procurement and overall subsistence, and also to derive more detailed coastal paleoecological data. The results show a predominantly terrestrial diet, while shellfish collection persisted amid prevailing environmental factors affecting mussel growth by supplementing their reduced mollusk takes with additional prey. Sizeable crustaceans were also procured in relatively large numbers in some localities, but not in all. This is the most-up-to date mid-Holocene subsistence record for the central west coast of South Africa which, apart from reconstructing changes in procurement strategies, reveals a trajectory of persistence in the face of climate change.

From diurnal to nocturnal activity: a case study of night-light niche expansion in Agama agama lizards

Most species of lizard are either diurnal or nocturnal, and it is extremely rare to find species that operate both diurnally and nocturnally, or that may shift from diurnality to partial nocturnality when conditions allow. However, niche expansion from diurnal to nocturnal habits (often referred to as the night-light niche) has rarely been reported in lizards (mainly in Anoles), and mostly through anecdotal reports. In West Africa, the rainbow lizard Agama agama is a conspicuous species across the region but also lives in suburban areas of towns and villages. It is a diurnal sun-basker operating at relatively high body temperatures of 36 °C and higher. In this paper, we describe a night-light niche expansion, i.e. nocturnal foraging and thermoregulation, in a small number of A. agama populations living in suburban areas. These lizards utilised radiant heat from incandescent light bulbs situated on the walls of buildings to mostly achieve target body temperatures and forage for and fed on five different groups of invertebrates. Foraging lizards had significantly higher body temperatures than inactive lizards. However, variance in body temperature was significantly greater in foraging lizards than in inactive lizards probably due to the necessity to shuttle between the incandescent night lights and cooler foraging areas during activity, a known cost of thermoregulation. Regression analysis of body temperatures against time of night in foraging lizards supported the notion that the lizards were maintaining body temperatures by actively thermoregulating whilst in inactive non-basking resting lizards during the same time period body temperatures declined. Although our results indicate a potential thermoregulatory benefit from using the night-light shift, we cannot be certain that this benefit is the direct cause of the shift, rather than an additional advantage when foraging.

Neutral and niche‐based factors simultaneously drive seed and invertebrate removal by red harvester ants

1. The factors that drive resource removal by insect predators hold the clue to understanding their role in structuring ecological communities and their evolution. Harvester ants are formidable seed predators and invertebrate carcass feeders. However, the extent to which neutral and niche‐based factors drive the selection and removal of preferred food resources by such ants has been neglected in the literature.2. In this study authors evaluated how the richness of plants and their abundance, along with resource proximity, density, nutrient content, and seasonal changes affect the selective harvest of resources by the harvester ant Pogonomyrmex barbatus in a Neotropical semi‐arid region where resource availability changes across rainy and dry seasons.3. In accordance with the neutral‐niche theory shaping biotic interactions, the authors observed that P. barbatus more frequently collects the seeds of the most abundant plant species located within their foraging areas, both in the dry and rainy seasons. The authors also observed that resources located in the proximity of nests, and those that are available at high density, are removed more often in the dry, whereas protein‐rich resources located at close range were removed most often in the rainy (i.e. niche‐based factors). Moreover, temporal fluctuations in the collection of seeds and invertebrates by P. barbatus suggest that the phenology of plants is a factor that can affect the availability and collection of resources.4. The findings exemplify how the dynamics between an insect predator and its food resource can be simultaneously explained by both neutral and niche‐based factors.

Inter-Specific and Intra-Specific Competition of Two Sympatrically Breeding Seabirds, Chinstrap and Gentoo Penguins, at Two Neighboring Colonies.

Simple SummaryUnder limited resources, different species may coexist by segregating their food items and foraging time, but neighboring colonies within the same species may have highly overlapping foraging habits. Thus, it is hypothesized that intra-specific competition is more intense than the inter-specific competition. To test this hypothesis, we chose sympatrically breeding Chinstrap and Gentoo penguins at two neighboring colonies and tracked their foraging space and dive depths during chick-rearing. Here we report that there was a larger overlap in the foraging space between the two species than within each species, whereas there was lower inter-specific isotopic niche overlap than intra-specific isotopic niche overlap. Despite the low intra-specific spatial overlap, diets of conspecifics remained similar, resulting in the higher isotopic niche overlaps. Our results suggest that intra-specific competition is higher than inter-specific competition due to a lack of niche partitioning.Theory predicts that sympatric predators compete for food under conditions of limited resources. Competition would occur even within the same species, between neighboring populations, because of overlapping foraging habits. Thus, neighboring populations of the same species are hypothesized to face strong competition. To test the hypothesis that intra-specific competition is more intense than inter-specific competition owing to a lack of niche partitioning, we estimated the foraging area and diving depths of two colonial seabird species at two neighboring colonies. Using GPS and time-depth recorders, we tracked foraging space use of sympatric breeding Chinstrap and Gentoo penguins at Ardley Island (AI) and Narębski Point (NP) at King George Island, Antarctica. GPS tracks showed that there was a larger overlap in the foraging areas between the two species than within each species. In dive parameters, Gentoo penguins performed deeper and longer dives than Chinstrap penguins at the same colonies. At the colony level, Gentoo penguins from NP undertook deeper and longer dives than those at AI, whereas Chinstrap penguins did not show such intra-specific differences in dives. Stable isotope analysis of δ13C and δ15N isotopes in blood demonstrated both inter- and intra-specific differences. Both species of penguin at AI exhibited higher δ13C and δ15N values than those at NP, and in both locations, Gentoo penguins had higher δ13C and lower δ15N values than Chinstrap penguins. Isotopic niches showed that there were lower inter-specific overlaps than intra-specific overlaps. This suggests that, despite the low intra-specific spatial overlap, diets of conspecifics from different colonies remained more similar, resulting in the higher isotopic niche overlaps. Collectively, our results support the hypothesis that intra-specific competition is higher than inter-specific competition, leading to spatial segregation of the neighboring populations of the same species.

Predation risk effects on intense and routine vigilance of Burchell's zebra and blue wildebeest

Prey increase vigilance to maximize predator detection, but this comes at the expense of foraging depending on the vigilance type: (1) intense vigilance, when all feeding processes are ceased, and (2) routine vigilance, when animals continue chewing (i.e. lower foraging cost). Few studies have distinguished between vigilance types when examining the effects of predation risk and, in the absence of a commonly accepted conceptual framework, the variables used to define predation risk vary greatly between studies. We investigated the relative importance of four predation risk categories (risky place assessed at the landscape and habitat level, vegetation characteristics at foraging site level, prey characteristics and resource availability) for the time spent on intense and routine vigilance by Burchell's zebra, Equus quagga burchellii, and blue wildebeest, Connochaetes taurinus taurinus, under predation risk from reintroduced predators, lions, Panthera leo. The risk categories each represented a different predation risk component and included metrics that defined the component at multiple scales. Intense vigilance responses were scale dependent, with zebra responding to a risky place at the landscape level and wildebeest to vegetation characteristics at a foraging area scale. Yet both species were able to adjust and balance time spent on vigilance types. Prey characteristics reduced the intense vigilance of wildebeest as herd size increased. Both species maintained similar levels of intense vigilance between seasons, despite lower resource availability, and thus higher foraging costs, in the dry season. However, the reduction in grass quality probably resulted in the increase in routine vigilance by both species during the dry season, as more time was needed to chew grasses with high fibre content. Our findings suggest different underlying mechanisms for the two types of vigilance behaviour, which were influenced by the ecology of the species, and demonstrate the importance of distinguishing vigilance types in predation risk studies.

Assessment of heavy metal pollution and exposure risk for migratory birds- A case study of Caohai wetland in Guizhou Plateau (China).

Increasing heavy metal pollution in wetland ecosystems around the world pose significant health risks to waterbirds, especially the endangered species. We analyzed heavy metal pollution in bird foraging area of Caohai wetland in Guizhou Plateau (China), and used an integrated exposure risk model for assessing heavy metal (Cd, Pb, Cr, Ni, Zn, Sb) exposure risk in birds from the soil, water, plants and benthic invertebrates. There is considerable variation in the extent of heavy metal contamination across the different sampling sites, and Cd and Sb are the main contaminants. The mussel Anodonta showed greater heavy metal accumulation (except for Zn) compared to the snail species C.cathayensis. The different plant species also varied in terms of amount for accumulated heavy metals. The phytophagous together with omnivorous birds were exposed to Cd, Pb, Zn and Ni through plants rather than the soil, whereas the maximum Zn exposure in the omnivorous and carnivorous birds was through consumption of benthic invertebrates. Furthermore, the phytophagous black-necked cranes (Grus nigricollis) were less risk to heavy metal exposure compared to the omnivorous bar-headed goose (Anser indicus) and carnivorous ruddy shelducks (Tadorna ferruginea). The exposure risk of Cr (8.1) was highest, followed by Pb (5.1), Zn (3.8), Sb (1.0), Cd (0.33) and Ni (0.28). The heavy metal assessment heavy metal exposure risk for migratory birds should take into account the exposure from food and soil. Our findings provide new insights into developing measures to minimize heavy metal contamination in migratory birds.

Interactions between seabirds and pelagic squid‐jigging vessels in the south‐west Atlantic

Abstract The waters of the Patagonian Shelf in the south‐west Atlantic are nutrient rich, support large concentrations of wildlife, and are exploited by several fisheries, including the large Asian squid‐jigging fishery. Although the squid‐jigging fishery has previously been observed to have few problems with the accidental mortality of seabirds, the deliberate catch for consumption of seabirds by the crew has been identified as a possible issue. Four cruises were made between Uruguay and the Falkland Islands during 2005–2006 to quantify the impact of jiggers on seabirds from indirect observation platforms. Monitoring included closely approaching 116 jigging vessels and boarding seven for inspection. The use of non‐jigging fishing gear, either for catching fish or seabirds, was observed at the stern of 33 vessels. Twelve seabird carcasses were observed floating close to vessels during 13 days of monitoring. Although the results recorded here are not sufficient to put a confident estimate on the magnitude of this mortality, the density of carcasses floating in the water among the jigging fleet indicated the potential significance of this problem. The results were considered sufficiently concerning for the Falkland Islands Government to take preventative actions, including educational efforts, improving humanitarian conditions onboard vessels, introducing relevant legislation and licence conditions, and prosecuting intentional seabird take inside the Falkland Islands jurisdiction. This has resulted in the apparent elimination of these mortalities within Falkland waters since the late 2000s. Nevertheless, it is likely that the same initial conditions exist for the crews of squid jiggers on vessels operating on the high seas, and so the possibility of the targeting of seabirds for consumption continues. Squid fisheries with substantial numbers of jiggers overlap with important foraging areas for a range of albatross and other species in high‐seas areas such as the Patagonian Shelf, the Humboldt and Kuroshio currents, and the south‐west Pacific Ocean. These areas of overlap may be important to investigate, especially in the foraging grounds of declining seabirds.

Breeding habitat selection of urban peregrine falcons (Falco peregrinus) in London

Abstract Understanding habitat selection by individual animals within their home range is crucial to facilitating their conservation. Peregrine falcon (Falco peregrinus) populations are increasingly urbanised, but little is known about their urban habitat use. In this study, we analysed the breeding habitat selection of peregrine falcons in London, United Kingdom, based on nest site locations identified through records of public sightings submitted to an online database between 2003 and 2018. We found peregrines displayed a preference for nesting in proximity to waterbodies, built-up areas and public parks and gardens, while wooded, agricultural and allotments areas were least preferred. We hypothesise that peregrines seek contrasting topography that proves advantageous for hunting in the vicinity of their nests, resulting in their selection of breeding sites within tall buildings that are adjacent to suitable foraging areas. From these findings, we conclude that (i) social drivers such as demand for green spaces and waterbodies near buildings shape peregrine nesting opportunities in the city and (ii) for urban planning to support conservation, we need further understanding of how each type of greenspace may be used differentially by raptors.

Sexual segregation of gannet foraging over 11 years: movements vary but isotopic differences remain stable

Sex-specific niche differentiation is common in marine vertebrates, but how this varies long-term is poorly understood. Here we investigated interannual variation in sexual segregation among breeding northern gannets Morus bassanus, wide-ranging central-place foragers with slight sexual dimorphism. Over 11 breeding seasons, we used GPS tracking and/or stable isotopes to test for sex differences in foraging trip characteristics (range, duration and timing); spatial distribution; habitat selection; and carbon and nitrogen isotopes in blood. When combining data from all years, females foraged further and for longer than males, yet despite this, the foraging areas of the sexes almost completely overlapped. Males and females selected foraging habitats that differed in terms of oceanography but not fishing vessel density. We also detected temporal segregation: females were more likely to be at sea during the day than at night, while males were more likely to be at sea during the night. However, foraging behaviour quantified by all GPS analyses varied interannually, with sex differences detected in some years but not others. Finally, males had consistently higher red blood cell δ13C and δ15N than females across all years, which was not driven by size dimorphism, instead likely by prey choice or very fine-scale habitat selection. We conclude that environmental variation influenced short-term sex differences in movement, but sex differences in stable isotopes that integrate behaviour over longer periods reveal more consistent differences. Our results suggest that inferences drawn from single-year studies may not relate to general patterns, highlighting the importance of long-term studies and combining methods.

Revenue efficiency, profitability, and profitability potential on organic versus conventional dairy farms—results from comparable groups of farms

The purpose of this paper is to explore whether differences in profitability and revenue efficiency exist between Norwegian organic and conventional dairy farms. With access to accountancy data from more than 1000 conventional farms, it was possible to compare the 59 organic farms with a matched group of 177 conventional farms. The two groups did not differ significantly with respect to share of turnover from milk, forage area, number of cows, milk quota, location, and share of robotic milking. Data spanned over the fiscal years 2014 to 2016. Stochastic frontier analysis was used to calculate revenue efficiency. The results confirmed that organic farms and conventional farms use different production technology, and therefore, we calculated efficiency on two different production frontiers. On average, organic dairy farms were 6.5 percentage points more revenue efficient than conventional farms. Although conventional farms appeared more profitable than organic farms, differences were not significant; however, conventional farms had a higher profitability potential than organic farms.

Sabellariid (Polychaeta: Annelida) reefs as nursery ground for the hermit crab Clibanarius symmetricus (Randall, 1840) on the Amazonian coast of Brazil

ABSTRACT The present study investigated the structure of the crab Clibanarius symmetricus (Randall, 1840) population found in a biogenic reef formed by the polychaete Sabellaria wilsoni Lana & Gruet, 1989 on the Amazonian coast. The population was sampled over a one-year cycle on a reef located in the mesolittoral zone of a sandy beach. The mean and maximum size of the crabs collected on the reef were smaller than those recorded in other tropical and subtropical coastal habitats, given that most of the specimens collected were immature (undetermined sex juveniles and sexually immature adults). Thaisella coronata (Lamarck, 1816) was the gastropod species whose shells were most occupied by the hermit crabs (70% of the specimens), although the smallest juveniles have used more the shells of other species. The results of the study suggest that C. symmetricus uses the reef as a nursery habitat, with bimonthly peaks in density that reflect recruitment periods. The sexually mature adults appear to use the reef only as a foraging area and, occasionally, as a refuge. The results demonstrated the importance these reefs on the population biology of this species and supports the need for more detailed monitoring studies and conservation actions for these habitats.

Normalizing home ranges of immature Kemp’s ridley turtles (Lepidochelys kempii) in an important estuarine foraging area to better assess their spatial distribution

ABSTRACT Kemp’s ridley turtles (Lepidochelys kempii) are critically endangered sea turtles that forage seasonally in Chesapeake Bay, a large estuary on the east coast of the United States. Most of the Kemp’s ridley turtles foraging in the bay are immature. When tracking these animals, satellite transmitter retention times have been low compared with adult marine turtles of other species. The immature Kemp’s ridleys’ small size and rapid growth leads to shorter, more variable deployments, limiting the use of data. These limited data leave critical questions remaining about the animals’ habitat usage that are difficult to answer without substantially more deployments. A novel sensitivity analysis using simulated deployments indicated that too few animals were tagged with satellite transmitters to identify all possible home-range areas in the Bay. We used simulation to create animal deployments of equal duration to address biases (differing lengths of deployments and time between locations) in home-range analyses and boost the information available from relatively short deployments. Combined home ranges from simulated deployments identified important areas for these animals in the south-western portions of the Chesapeake Bay and in the nearshore areas of the Bay north to the middle of the Bay. These areas represent opportunities for managers to mitigate impacts from boating, dredging, military activities and fishing, and could inform critical habitat designations under the United States Endangered Species Act. Habitat modelling may be needed to identify additional important areas in the Bay where animals were not observed via satellite tracking.