Simulating cryptic movements of a mangrove crab: Recovery phenomena after small scale fishery (original) (raw)
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Potential bottom-up control of blue crab distribution at various spatial scales
2003
A B S T R A C T Top-down (i.e., predation), bottom-up (i.e., food availability), and physical factors may influence blue crab (Callinectes sapidus) distribution. To assess the role of bottom-up and physical process in blue crab distributions, we concurrently measured density of the blue crab (Callinectes sapidus), density of its principal prey, the Baltic clam (Macoma balthica), and physical characteristics in mud and sand habitats spanning various spatial scales (1-10 km and 10-50 km) in the York River, Chesapeake Bay. Clam and crab densities were intermediate in mud, low in downriver sand, and high in upriver sand. Clam and crab densities were not correlated in mud, whereas in sand, they were significantly and positively correlated at both the local scale (1 km) and at the broadest spatial scale (10-50 km). Crab density also correlated with salinity at the broad spatial scale. After removing the effect of salinity, crab density remained significantly correlated with clam density. Using a hydrodynamic model for the York River, potential transport of clams from downriver coves was primarily to upriver habitats, but transport of crabs was mainly to downriver seagrass habitats. At the local scale, upriver zones where crab and clams were abundant, crab density was highly correlated (r 2 ϭ 0.93) with clam density, but not with salinity, suggesting that the distribution of blue crabs was driven mostly by their primary food item-clams. The collective findings are consistent with the hypotheses that crab density is driven by both food availability and salinity at broad spatial scales (10-50 km), whereas food availability is a primary control at smaller spatial scales (1-10 km). Bottom-up control of upper trophic levels may be distinctive; thus far, in marine and freshwater systems, bottom-up control has not been demonstrated to filter from basal to upper trophic levels. Furthermore, unvegetated habitats where food, such as clams, is abundant may be important in the population dynamics of the blue crab, even in systems where seagrass beds are common.
Spatial structure of a leaf-removing crab population in a mangrove of North-Brazil
Wetlands Ecology and Management, 2009
The leaf-removing decapod crab, Ucides cordatus plays a key role as ecological engineer in Brazilian mangrove ecosystems. We analyzed the spatial distribution of a specific population at two different scales to observe how individual behavior could alter spatial population structure. First, we conducted a spatial point pattern analysis of the burrow entrances and the Rhizophora mangle prop roots on the mangrove floor at a scale of few meters. Secondly, we analyzed at a large scale (10–100 m) the potential effects of surface elevation, light intensity, prop root coverage, species of neighboring tree (R. mangle, Laguncularia racemosa, Avicennia germinans) and pneumatophore density on the size and number of burrow entrances. At the same large scale, we conducted an analysis of clustering of the crabs around the R. mangle trees. At small scale, the burrow entrances, although aggregated around the prop roots, showed a regularly spaced distribution (∼25 cm) signaling an intraspecific competition among the crabs. At large scale, crabs preferred to install their burrows at an intermediate level of surface elevation and prop root coverage, and in R. mangle-dominated areas. At the same kind of habitats, the largest burrows, and thus potentially the largest crabs, were found in higher number than on other habitats. The R. mangle-dominated areas preference was confirmed by an aggregating around R. mangle trees in R. mangle-dominated forest, but only of large individuals in L. racemosa-dominated forest. These observations lead us to the definition of a preferred habitat for U. cordatus. Competition leading to the small-scale regular patterns was proposed as an explanation for exclusion of smaller crabs from preferred habitats seen at large scale. We hypothesize that this preferred habitat might explain at regional scale the variation of U. cordatus importance in Neotropical mangroves.
Modelling the dynamics of invasion and control of competing green crab genotypes
Theoretical Ecology, 2014
Establishment of invasive species is a worldwide problem. In many jurisdictions, management strategies are being developed in an attempt to reduce the environmental and economic harm these species may cause in the receiving ecosystem. Scientific studies to improve understanding of the mechanisms behind invasive species population growth and spread are key components in the development of control methods. The work presented herein is motivated by the case of the European green crab (Carcinus maenas L.), a remarkably adaptable organism that has invaded marine coastal waters around the globe. Two genotypes of European green crab have independently invaded the Atlantic coast of Canada. One genotype invaded the mid-Atlantic coast of the USA by 1817, subsequently spreading northward through New England and reaching Atlantic Canada by 1951. A second genotype, originating from the northern limit of the
Interference competition as a key determinant for spatial distribution of mangrove crabs
BMC ecology, 2018
The spatial distribution of mangrove crabs has been commonly associated with tree zonation and abiotic factors such as ground temperature and soil granulometry. Conversely, no studies were designed to investigate the role of competition for resources and predation in shaping crab distribution in mangroves, despite these biotic factors are recognised as key determinants for spatial patterns observed in the communities colonising rocky and sandy intertidal habitats.We studied floral and faunal assemblages in two zones of a Sri Lankan mangrove, a man-made upper intertidal level and a natural eulittoral, mid-shore one. Leaf choice experiments were designed to study both feeding rate and intra and inter-specific interactions for food of sesarmid crabs in the two habitats in order to better understand crab spatial distribution. The two intertidal belts differed in terms of floral composition and crab species abundance. The eulittoral zone was strongly dominated by Neosarmatium smithi, whi...
Green crab larval retention in Willapa Bay, Washington: an intensive Lagrangian modeling approach
Estuaries and Coasts, 2009
The European green crab (Carcinus maenas) is invasive on the U.S. West Coast. This study uses a highresolution circulation model to determine the likelihood that green crab larvae spawned in Willapa Bay, Washington could be retained by circulation and behavior long enough to reach maturity and resettle within the bay. A particletracking method (the "diffusive Lagrangian return map") is presented that makes it possible to track the dispersion of hundreds of thousands of model larvae-each subject to three-dimensional advection, vertical turbulent diffusion, and imposed vertical migration behavior-over their full 30-50 days development time with modest computational resources. Larvae spawned in summer show significant retention (5-40%) in the southern and western portions of the bay, including the Stackpole shoals near the mouth, the area most likely to be colonized by late-stage megalopae arriving from the coastal ocean. Larvae spawned in spring show much less retention throughout the bay because of (1) increased flushing caused by increased river input relative to summer conditions and (2) longer development times caused by lower water temperatures. The role of larval swimming behavior is secondary to hydrodynamics in setting these spatial and seasonal patterns of retention.
Environmental Reviews, 2016
Environmental factors determine the habitat selection, use and distribution of species at various spatial scales. Understanding the factors driving these distributions can help predict areas of higher species occurrence, and be used in species conservation, and management strategies. In this study we reviewed 71 publications to evaluate the most relevant factors shaping local, finescale distribution of a globally invasive species, the European green crab (Carcinus maenas). We compared these studies to determine how factors differ (i) between adult and juvenile life stages, (ii) with the influence of internal and temporal variables, and (iii) among clades. Factors of depth, biotic interactions, vegetation, presence of shelter and salinity were found to be important, although the supporting evidence varied between juvenile and adult stages. Internal variables of size, carapace color and sex, and temporal variables such as seasonal, tidal and diel cycles played a role in determining how crabs responded to environmental factors. The importance of environmental factors also varied by clade. All of these factors and variables may be expected to play a role in the local, fine-scale distribution of C. maenas. These variations affect the efficacy of using a single model to anticipate local green crab distribution (e.g., spatial distribution model). Application of different models for adult and juvenile subsets of the population, clades, and accounting for temporally shifting distribution may help accommodate some of this variation. The relative presence of factors in a region and the availability of local, fine-scale environmental data may further influence the efficacy of modeling. The combined effects of such considerations will make predictive local modeling at fine scales challenging, if not impossible, with existing knowledge, data and technology. Nonetheless, our results provide insight into the environmental characteristics most relevant to shaping local distributions of C. maenas, which may inform management strategies such as
A bioenergetics model was developed and applied to questions of habitat use and migration behavior of nonindigenous European green crab (Carcinus maenas) in Willapa Bay, Washington, USA. The model was parameterized using existing data from published studies on the ecology and physiology of C. maenas and allied brachyuran crabs. Simulations of the model were run describing four scenarios of habitat use and behavior during a 214-d simulation period (April–October) including crabs occupying mid littoral habitat, high littoral habitat, sublittoral habitat, and sublittoral habitat but undertaking intertidal migrations. Monthly trapping was done along an intertidal gradient in Willapa Bay to determine the actual distribution of crabs for the same time interval as the simulation period, and model results were compared to the observed pattern. Model estimates suggest no intrinsic energetic incentive for crabs to occupy littoral habitats since metabolic costs were c. 6% higher for these individuals than their sublittoral counterparts. Crabs in the littoral simulations were also less efficient than sublittoral crabs at converting consumed energy into growth. Monthly trapping revealed that C. maenas are found predominantly in mid littoral habitats of Willapa Bay and there is no evidence of resident sublittoral populations. The discrepancy intimates the significance of other factors, including interspecific interactions, that are not incorporated into the model but nonetheless increase metabolic demand. Agonistic encounters with native Dungeness crabs (Cancer magister) may be chief among these additional costs, and C. maenas may largely avoid interactions by remaining in littoral habitats neglected by native crabs, such as meadows of nonindigenous smooth cordgrass (Spartina alterniflora). Adult C. maenas in Willapa Bay may occupy tidal elevations that minimize such encounters, and metabolic costs, while simultaneously maximizing submersion time and foraging opportunities.
Marine Ecology Progress Series, 2009
Identifying the key determinants of benthic predator distributions is crucial in understanding the dynamics of predator and prey populations in intertidal environments. In this paper, we assessed the roles of predator morphology, prey availability and competition in determining the distribution of an important benthic predator, the shore crab Carcinus maenas (L.). The abundance of shore crabs at high tide on 3 intertidal mudflats in the Dutch Wadden Sea was assessed in relation to distance to the nearest gully, size, sex and colour of the crabs. Furthermore, food availability (bivalves, crustaceans, polychaetes) in the sampling sites was measured. Half of all crabs were found in the gullies adjacent to each mudflat, where the abundance of a prey species (the large brown shrimp Crangon crangon) was also highest. The spatial distribution of crabs between the gullies and the mudflats depended in an interactive way on the colour morph and sex of individuals. Comparing observed distributions of crabs with those predicted from a recently developed ideal free distribution model showed that crabs did not distribute themselves optimally in terms of maximising food uptake and minimising the strength of competition from conspecifics. The results highlight the yet underrated role of shore crabs as a potentially important predator of shrimps, and the need to incorporate morphological characteristics and different prey types into ideal free distribution models to test the optimal foraging behaviour of benthic crabs.
California Cooperative Oceanic Fisheries Investigations Reports, 2007
Accounting for species interactions is a key component of ecosystem-based management. Simple models of species interactions provide a framework for making qualitative comparisons and identifying critical dynamics. A review of multispecies-fisheries and marine-reserve models indicates that incorporating species interactions leads to decreased theoretical predictions for sustainable yield and harvest rates and to increased theoretical predictions for the reserve size necessary to protect populations; ontogenetic shifts in interactions also have a significant effect on multispecies model predictions. While previous models have explored negative species interactions (i.e., predation and competition), this paper presents an example marine reserve model with a positive interaction: a spiny lobster-sea urchin-red algae trophic chain where red algae facilitate lobster recruitment. Model results indicate that recruitment facilitation primarily affects the time scale of the species dynamics a...