Crab Abundance Research Articles

Larval trematodes infecting the South-American intertidal mud snail Heleobia australis (Rissooidea: Cochliopidae)

Larval trematodes infecting the snail Heleobia australis (Cochliopidae) from the Bahía Blanca estuary, Argentina were surveyed for two years. A total of 7,504 snail specimens was dissected and the larval stages of 15 different trematodes were recovered and examined morphologically. These larvae included four species that had previously been reported from H. australis in Brazil, Uruguay, and Argentina: the heterophyid Ascocotyle (Phagicola) longa and the microphallids, Maritrema bonaerense, Maritrema orensense, and Microphallus simillimus. Three other species, the echinostomatid Stephanoprora uruguayensis, the microphallid Levinseniella cruzi, and the psilostomid Psilochasmus oxyurus are reported here for the first time as parasites of H. australis. Eight other trematodes found in H. australis are described and placed in the appropriate superfamilies, families or genera (Cryptogonimidae, Apocreadiidae, Aporocotylidae, Notocotylidae, Haploporidae, Renicolidae, Himasthla, and Renicola). The prevalence of the trematode taxa infecting H. australis in the Bahía Blanca estuary was low (<3%) with a single exception (M. simillimus; >20%). Microphallidae were the richest and the most prevalent family, probably because of the high abundance of crabs - the second-intermediate hosts of certain microphallid species - and the considerable diversity of gulls. Here we compare the parasite assemblage found in the H. australis from Bahía Blanca estuary with other parasite assemblages infecting Heleobia spp. and other rissooids from the rest of the world.

Ontogenetic distribution of Callinectes ornatus (Decapoda, Portunoidea) in southeastern Brazil

The spatial and seasonal distribution of different demographic groups of the swimming crab Callinectes ornatus was analyzed with respect to its population biology in three bays (Ubatumirim, Ubatuba, and Mar Virado) in southeastern Brazil. In each bay, monthly sampling was performed during two years along six transects, established at 5, 10, 15, and 20 m depth (parallel to the beach line), in a wave-sheltered area (7.5 m depth), and at an exposed site (10 m depth). Total abundance of crabs was similar among the bays. The presence of immature individuals, adult females, and breeding females was positively correlated with the bottom and surface temperatures, whereas adult males showed an opposite trend with respect to these factors. Immature and smaller individuals were most abundant along the sheltered and shallower transects. Males were more abundant along the shallower transects, and females at 15 and 20 m. This study revealed that different demographic groups occupy the habitat in different ways, according to local features. In general, southeastern Brazil offers a range of conditions that favor reproduction and consequently the maintenance and growth of the local population of C. ornatus, contributing to the relatively high abundance of the species in this coastal area.

Effect of natural disturbance on migrations and population dynamics of a catadromous species, Eriocheir japonicus, along the Lo-Mei stream in northern Taiwan

Japanese mitten crab, Eriocheir japonicus (de Haan), migrates between stream and sea and breeds in shallow coastal areas, exhibiting a catadromous life cycle. This study investigated how the crabs adjust reproductive strategy and migratory behavior to climate fluctuation and what kind of life history strategy individual crabs adopt in a disturbed environment. We conducted a 14-year monitoring study from 1998 to 2011 in Lo-Mei Stream in northern Taiwan. Streamflow and flood timing are controlled by precipitation and typhoons. Abundance of crabs was lower after disturbances by several typhoons and by lower temperatures associated with cold winters in 2006 and 2007. Samples from 2003 showed a reversal in reproductive trends, with increasing size in the same pattern of oocytes, compared to reproductive biology from 1999 to 2005. The life history of E. japonicus can be divided into three stages: spawning migration, growth period, and upstream migration of juveniles to compensate for downstream migration of mature crabs. Reproductively, in E. japonicus the combination of semelparity and synchronous breeding can increase reproductive potential and increase survival in a less disturbed environment at the optimum time. Environmental cues play an important role as major triggers in the persistence of populations.

Return of the Native: Historical Comparison of Invasive and Indigenous Crab Populations Near the Mouth of Delaware Bay

ABSTRACT An invasive population of the Asian shore crab Hemigrapsus sanguineus was discovered in 1988 near the mouth of Delaware Bay, and populations now occur from North Carolina to Maine. The shore crab H. sanguineus competes with indigenous species and has displaced resident crabs throughout its invasive range. However, there have been few studies that document changes in populations of H. sanguineus after the species has become established.We compare sympatric populations of the Asian shore crab and a native mud crab (Panopeus herbstii) that were monitored initially in 2001 and again in 2011 and 2012. The historical study was conducted in a rocky habitat near Cape Henlopen at the southern terminus of Delaware Bay (38.793° N, 75.158° W). Results showed large differences in the relative abundance of the two species throughout the duration of the study. The Asian shore crab H. sanguineus accounted for 75% of total crab abundance in 2001, but abundance had decreased to less than 25% in both 2011 and 2012....

Fishers' choice of alternative management scenarios: A case study in the Danajon Bank, Central Philippines

The lack of general understanding that fisheries is an integral part of a larger and dynamic ecosystem can lead more to highlighting the conflicts, rather than realizing the real interaction between the economic, social, and ecological objectives of fisheries management. Furthermore, the poor grasp for the motivations underlying the fishers' behavior in their response to fisheries issues, policies, and regulations may have contributed to many failed fisheries management endeavors. This paper presents the results of a stated preference survey administered to 422 small-scale fishers in the coastal municipality of Talibon, Bohol of the Danajon Bank, Central Philippines, whereby fisheries management was likened to a commodity or good that satisfies the fishers' needs. The study tested specific attributes representing the economic, social, and ecological objectives of fisheries management that are likely to influence the fishers' attitudes toward a management strategy. The attitudes were elicited from the fishers' preference for a particular hypothetical management scenario over another in a series of choice games. A logistic model demonstrated high probabilities of choice when a management strategy promotes the increase in effort of fishing gear types perceived to be least harmful to the marine ecosystem, increases overall fisheries harvest, secures employment security for the majority, and increases the abundance of blue crabs – an important fisheries commodity in the Danajon Bank area. Key socio-economic and socio-civic characteristics of the fishers and their general knowledge, attitudes to, and perceptions of fisheries ecology concepts and fisheries management issues were likewise identified as probable determinants of choice and therefore behavior – such as acceptance or support – toward actual fisheries management policies.

Response of mangroves to drought and non-tidal conditions in St Lucia Estuary, South Africa

The effect of a prolonged closed-mouth state on the condition of mangrove habitats was studied in May 2010 at St Lucia Estuary, KwaZulu-Natal. The mouth had been closed to the sea since 2002 as a result of artificial mouth closure and drought, which had resulted in non-tidal, dry and hypersaline aquatic conditions. Sediment characteristics, mangrove population structure, and snail and crab abundance, were measured at four sites of differing salinity and water level to determine if there was a relationship between environmental characteristics and biotic response. A site fringing the main channel had the lowest elevation and the highest density of mangrove seedlings and saplings at the water's edge, whereas a dry site at the highest elevation had the lowest density of mangroves with mostly tall adult trees and few saplings. At these two sites the salinity (>34.5) was significantly higher and the surface sediment water content (<30%) was significantly lower than at other sites. Highest tree density was found at a freshwater seepage site, where all size classes were represented, while the permanently flooded site between the Mfolozi River and St Lucia Estuary had the tallest trees but no seedlings or saplings. At the freshwater seepage and permanently flooded sites, porewater and sediment salinity (<10) were significantly lower, while sediment moisture (>55.5%) was significantly higher, than at the fringing and dry sites. Low sediment moisture was unfavourable for mangrove growth and recruitment. Long-term monitoring is needed to document the response of the mangroves to closed-mouth, non-tidal conditions.

Invasive mangrove removal and recovery: Food web effects across a chronosequence

Red mangrove (Rhizophora mangle) was introduced to Hawai'i in 1902 and has since overgrown many coastal areas in Hawai'i, transforming nearshore sandy habitat into heavily vegetated areas with low water velocity, high sedimentation rates, and anoxic sediments. Introduced mangrove forests provide habitat for exotic species, including burrowing predators, which can exert top-down effects on benthic communities. Removal of mangrove overstory is a popular management technique, and, here, we study community change over a chronosequence of mangrove removals from 2007 to 2011, investigating infaunal community structure, crab abundance, and response to predator exclusion in the presence of mangrove overstory and along the chronosequence of removals. Overstory removal results in gradual changes in community composition concurrent with slow decomposition of sedimentary mangrove biomass (k=0.36±0.06×10−3d−1). Changes over time after removal include an increase in total infaunal abundance, a decrease in sub-surface deposit feeders, and an increase in suspension-feeding worms. Burrowing crab densities are uniform across mangrove and removal sites, and, unlike in native mangroves, their effects on infaunal communities are similarly negligible in both mangrove and removal areas. These results show that recovery from invasion and removal occurs gradually and is not governed by top-down effects.

Regional Ontogeny of New England Salt Marsh Die-Off

Coastal areas are among the world's most productive and highly affected ecosystems. Centuries of human activity on coastlines have led to overexploitation of marine predators, which in turn has led to cascading ecosystem-level effects. Human effects and approaches to mediating them, however, differ regionally due to gradients in biotic and abiotic factors. Salt marsh die-off on Cape Cod, Massachusetts (U.S.A.), triggered by a recreational-fishing-induced trophic cascade that has released herbivorous crabs from predator control, has been ongoing since 1976. Similar salt marsh die-offs have been reported in Long Island Sound and Narragansett Bay (U.S.A.), but the driving mechanism of these die-offs has not been examined. We used field experiments to assess trophic interactions and historical reconstructions of 24 New England marshes to test the hypotheses that recreational fishing and predator depletion are a regional trigger of salt marsh die-off in New England and that die-offs in Long Island Sound and Narragansett Bay are more recent than those on Cape Cod. Predator depletion was the general trigger of marsh die-off and explained differences in herbivorous crab abundance and the severity of die-off across regions. Die-offs in Long Island Sound and Narragansett Bay are following a trajectory similar to die-off on Cape Cod, but are approximately 20 years behind those on Cape Cod. As a result, die-off currently affects 31.2% (SE 2.2) of low-marsh areas in Long Island Sound and Narragansett Bay, less than half the severity of die-off on Cape Cod. Our results contribute to the growing evidence that recreational fishing is an increasing threat to coastal ecosystems and that studying the effects of human activity at regional scales can provide insight into local effects and aid in early detection and potential remediation.

Optimal Allocation of Sampling Effort in Depletion Surveys

We consider the problem of designing a depletion or removal survey as part of estimating animal abundance for populations with imperfect capture or detection rates. In a depletion survey, animals are captured from a given area, counted, and withheld from the population. This process is then repeated some number of times at the same location and the decreasing catches of the local population inform jointly local abundance and the capture or detection rate, which we call catchability. The aim of such a survey may be to learn about the catchability process, and this information may then be applied to a broader survey of the population so as to accurately estimate total abundance. In this manuscript we consider the problem of how to optimally allocate sampling effort at the depletion sites. Allocating sampling effort involves determining how many times to repeat the depletion process at a given site versus how many different sites to include in the sampling. By maximizing the Fisher information of the parameter describing catchability as a function of the survey design, we attempt to estimate the optimal number of depletions per site, which depends on the catchability value itself. We also discuss other aspects of depletion sampling apparent from the derivation of Fisher information, including the difficulties of sampling with low catchability values (e.g. below 0.15), and we consider our results with respect to the annual Chesapeake Bay blue crab abundance survey conducted by the Maryland Department of Natural Resources.

Brachyuran and anomuran crabs associated with Schizoporella unicornis (Ectoprocta, Cheilostomata) from southeastern Brazil

The main goals of this investigation were to describe the community structure of anomuran and brachyuran crabs inhabiting reefs constituted by colonies of Schizoporella unicornis, and to provide a species importance ranking for this community. Collections were carried out on S. unicornis reefs at two-month intervals from May 2003 to May 2004, in the rocky sublittoral of the southeastern Brazilian coast. Relative abundance and occurrence were used to rank these species in the hierarchy importance. A total of 2,018 individuals were obtained, in 11 families, 22 genera and 31 species. Porcellanidae and Pilumnidae were the most abundant families, comprising respectively almost 60% and 15% of individuals sampled. The species ranking indicated four main groups A, B, C and D, with group A subdivided. Subgroup A1 contained 9 species, including the species of greatest ecological importance for community regarding abundance and occurrence. The great abundance of crabs associated with S. unicornis seems to be the result of its recognized importance during the crab developmental cycle, and as shelter and food for some Decapod species. These observations reveal the importance of conserving the areas occupied by these reef colonies, which appear to be an important environment for maintaining local biodiversity.

Characterizing coastal foodwebs with qualitative links to bridge the gap between the theory and the practice of ecosystem-based management

Abstract Tools that integrate the complexity of natural systems are needed to facilitate ecosystem-based management (EBM). Loop analysis is an underutilized qualitative tool for EBM that uses information on foodweb links (e.g. predator–prey interactions) and the resulting pathways (cycles) through the foodweb to predict responses to press perturbations. We explore the utility of loop analysis related to management actions: increasing crab abundance and reducing eutrophication in coastal foodwebs. We found that crab-related management actions propagated through the foodweb, with positive and negative impacts. Several negatively impacted species support important fisheries; their declines illustrate the challenge of developing multispecies plans. In our analysis, the management actions decreasing eutrophication reduced most functional groups. However, these predictions were unreliable, suggesting indiscernible bottom-up effects in the foodwebs. Simultaneously managing for crab increases and reducing eutrophication created mostly decreasing abundances in other functional groups and reduced the predictability of the responses. The response to each management action suggests trade-offs between goals, and the qualitatively unreliable predictions could result from variation in the strength of species interactions or indicate knowledge gaps. EBM can benefit from both the explicit articulation of trade-offs and the identification of gaps in our understanding of these systems.

Impacts of a large-bodied, apex predator (Alligator mississippiensis Daudin 1801) on salt marsh food webs

Large-bodied apex predators (e.g., sharks, wolves, crocodilians) are believed to regulate food web structure and drive ecosystem processes, but there remains relatively little experimental evidence. Here we use field surveys and a mesocosm experiment to evaluate the cascading effects of an apex predator (American alligator) on a salt marsh food web. Consistent with previous studies (n=10), field surveys revealed blue crabs (Callinectes sapidus Rathbun 1896), an important marsh mesopredator, were a frequent component of estuarine-occurring alligators' diet (mean±SD, 47±20%, n=1384). In mesocosms, we examined potential consequences of this interaction in a simplified salt marsh community. We experimentally isolated alligator effects on the abundance (consumptive effect) and behavior (non-consumptive effect) of blue crabs and on blue crab consumption of plant-grazing snails and ribbed mussels. Alligators reduced blue crab abundance by ~40% over 3days and induced behavioral changes, resulting in decreased foraging activity and increased refuge use by blue crabs. The combined effects of reduced crab abundance and altered behavior translated into increased survival of both a keystone grazer (snails) and a mutualist (mussels) within the salt marsh food web. Our findings experimentally demonstrate that a large-bodied, apex predator has the potential to 1) generate a trophic cascade, 2) elicit behavioral changes (i.e., non-consumptive effects) in mesopredator prey, and 3) indirectly affect the potential for both grazing and mutualism to occur in this food chain. Our results generate testable hypotheses regarding the broad-scale effects of alligator presence and top-down forcing in salt marsh ecosystems.

Lesser black-backed gulls (Larus fuscus) consuming swimming crabs: An important link in the food web of the southern North Sea

Swimming crabs (Liocarcinus spp.) are one of the most common brachyuran species in the North Sea, and their abundance has substantially increased over the last century. Seabirds such as lesser black-backed gulls (LBBG) commonly feed mainly on higher-trophic-level organisms such as fish. However, intensive use of swimming crabs by LBBGs in the eastern North Sea has been noted over several years. Our investigation of this aspect of the food web by examining food remains from breeding LBBGs showed that swimming crabs accounted for more than half of the nutrition of LBBGs. Gulls selected larger individuals than expected, based on sizes of free-living swimming crabs. A long-term data set (2002–2006) shows that gulls took swimming crabs mainly in the early morning and late evening, suggesting that they might migrate vertically in the water column. Moreover, it shows that although swimming crabs occurred at considerable distances from the shore, LBBGs took this prey item exclusively from near the shore where it was most abundant. This suggests the existence of a possible energy threshold above which gulls experience a net energy loss, if they have to travel too far from their colony, where the abundance of swimming crabs is lower and the energy intake might thus not compensate for the long-distance flights. Swimming-crab abundance did not appear to be the primary factor influencing overall gull distribution. A simple bioenergetic model showed that the 22,000 individual LBBGs in the most important breeding colony in the south-eastern North Sea consumed approximately 35 million swimming crabs annually (i.e. 1590 swimming crabs per individual gull) during the breeding period. However, considering the high numbers of swimming crabs in the south-eastern North Sea (demonstrated by bottom-trawl surveys in 2005 and 2007) LBBGs are unlikely to exert top-down control on this prey. Conversely, a bottom-up effect is more likely, potentially enabling further increases in LBBG populations through increases in their most important prey item in the south-eastern North Sea.

The relationship of blue crab abundance to winter mortality of Whooping Cranes

We sampled blue crab (Callinectes sapidus) numbers in marshes on the Aransas National Wildlife Refuge, Texas from 1998–2006, while simultaneously censusing the wintering population of Whooping Cranes (Grus americana) on the refuge and surrounding habitats. This was done to determine whether mortality of wintering Whooping Cranes was related to the availability of this food source. Yearly variation in crab numbers was high, ranging from a low of 0.1 crabs to a high of 3.4 crabs per 100-m transect section. Significant non-linear increases in both juvenile and adult mortality in relation to decreasing crab abundance was observed. Results suggest that some threshold of crab abundance exists in which Whooping Cranes have higher survival on their wintering grounds.

Spatio-temporal population genetic structure and mating system of red king crab (Paralithodes camtschaticus) in Alaska

Red king crab, Paralithodes camtschaticus Tilesius, 1815, an economically and culturally important species in the state of Alaska, experienced drastic reductions in abundance over large portions of their Alaskan range by 1980. Abundance of crabs in some of the most important historical fishing areas have failed to rebound, some even in the absence of fishing, highlighting the need for additional research to infer genetic structure and reproductive biology of the species that can then be used to inform management efforts. Red king crab samples were collected from eleven locations throughout Alaska ( n = 845 ), of these, six locations were sampled at least one generation apart. Results of this study suggest moderate rates of gene flow within the Gulf of Alaska/Western Alaska region. Levels of genetic differentiation among populations within Southeast Alaska were higher than seen elsewhere, and there was strong evidence of multiple distinct populations. Red king crab in Bristol Bay and in two areas in Southeast Alaska show signs of recent population bottlenecks and shifts in allele frequencies not observed in previous studies that used less polymorphic genetic markers. In addition to population genetic structure analyses, 24 female red king crab and their broods were collected for purposes of inferring mating system. There was no evidence of multiple paternity in any brood. The results of this study support continued management of distinct geographic groups within the Gulf of Alaska/Western Alaska region and suggest that finer-scale management may be beneficial in Southeast Alaska.

Influence of freshwater inflow on reproductive capacity of the mud crab Eurypanopeus depressus inhabiting oyster reefs

Oyster reefs provide structural habitat for resident crabs and fishes, the planktonic larvae of which rely on estuarine transport/retention mechanisms to ensure settlement and subsequent recruitment to reefs. During periods of high freshwater inflow, larvae can be advected downstream and flushed out onto the continental shelf, resulting in an apparent reduction of larval supply within the estuary. However, reduced larval densities in estuaries might also result from decreased reproductive capacity, as dilute salinities on reefs upstream stress adult crabs. This study examined the reproductive capacity of the mud crab Eurypanopeus depressus (Smith, 1869) in response to freshwater inflow using the percentage of ovigerous females present as an indicator. Reproductive capacity on reefs was compared between two sites located near the mouths of two tidal tributaries, each experiencing differing rates of freshwater inflow, and between wet and dry seasons. Abundances of juvenile and adult crabs were significantly reduced during the wet season and at the site experiencing greater freshwater inflow. Length-frequency data indicate that newly recruited juvenile crabs were much less abundant at the site experiencing higher rates of inflow. The percentage of ovigerous females present was also reduced during the wet season but only at the reef experiencing greater inflow. Furthermore, the percentage of ovigerous females present at this site was inversely related to freshwater inflow and positively related to salinity. We suggest that high rates of freshwater inflow and the concomitant reduction in salinity can limit reproductive capacity in the flatback mud crab E. depressus on oyster reefs. Nonetheless, even as reproduction may be inhibited on reefs experiencing high inflow, other reefs subjected to lesser inflow may continue to serve as a source of larvae.

Life-History Aspects of the Yellow Irish Lord (Hemilepidotus jordani) in the Eastern Bering Sea and Aleutian Islands

Growth, reproduction, and diet of the Yellow Irish Lord (Hemilepidotus jordani) were examined and compared between 2 adjacent geographical regions of Alaska, the eastern Bering Sea and Aleutian Islands, where its biology is not well understood. The Yellow Irish Lord is the most common member of the genus Hemilepidotus encountered during Alaska Fisheries Science Center bottom-trawl surveys of these regions. Based on our data, there was no significant difference in sizes of Yellow Irish Lords caught between regions. The von Bertalanffy growth models fitted to length-at-age data, however, indicate that male and female Yellow Irish Lords in the Aleutian Islands grew more slowly than those in the eastern Bering Sea. Histological assessment of ovary condition indicated that Yellow Irish Lords from both regions appear to spawn once annually during the summer. Relationships between size (length and weight) and fecundity between the 2 regions were significantly different, with Yellow Irish Lords from the Aleutian Islands being more fecund. Diet analysis showed that the Yellow Irish Lord is a benthic predator and their summer diets in both regions consist of a wide variety of prey, but appear to favor benthic crustaceans, particularly abundant crab species. However, the largest individuals appear to have more opportunities for piscivory in the Aleutian Islands. It appears that at least some variation in the life-history aspects of this species exists between these regions. This information may provide a scientific basis for developing management strategies of the Yellow Irish Lord in Alaskan waters.

Construction of biological reference points for management of the Dungeness crab, Cancer magister, fishery in the Fraser River Delta, British Columbia, Canada

The objective of this study was to define two biological reference points, the Upper Stock Reference Point (USR) and the Limit Reference Point (LRP), to facilitate management of the Fraser River delta commercial Dungeness crab (Cancer magister) fishery in a precautionary manner. The USR is the stock level below which the removal rate is progressively reduced to avoid reaching the LRP. The LRP is the stock level below which productivity is sufficiently impaired to cause serious harm. Currently, the commercial Dungeness crab fishery in the Fraser River delta is managed with a minimum size limit (165mm carapace width point-to-point), non-retention of females and soft-shell crabs, and a restricted fishing season (June to November) to protect large males during the winter/spring moult period. We evaluated variations in legal male, sublegal male, and female Dungeness crab abundances using fishery-independent trap surveys from 1988 to 2010. We also examined proportions of soft-shell legal male and female crabs using survey data and information collected from commercial fishing. A relationship existed between female abundance and corresponding legal male abundance five years later, which is well described by the Beverton–Holt stock–recruitment model. We conducted simulations to assess possible adverse impacts of fishing on the crab population. We assumed the population would stabilize at the existing abundance upon suspension of commercial harvesting if abundance has been steadily declining. Using the stock–recruitment relationship along with information on commercial catch compositions and soft-shell proportions, we assessed the potential reduction in legal male and female crab abundances, given persistent fishing, before the population reaches a lower equilibrium. The amount of reduction to legal male and female crabs increases with decreasing population size. If legal male crab abundance is 50% and 20% of maximum possible recruitment, then fishing would reduce female abundance by 20% and 48%, respectively, before the population is stabilized. We propose these two female abundance levels as the USR and LRP for managing the Fraser River commercial Dungeness crab fishery.

Spatio-temporal variations in invertebrate−cod−environment relationships on the Newfoundland–Labrador Shelf, 1995−2009

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 469:263-278 (2012) - DOI: https://doi.org/10.3354/meps10026 Spatio-temporal variations in invertebrate−cod−environment relationships on the Newfoundland–Labrador Shelf, 1995−2009 Matthew J. S. Windle1,*, George A. Rose1, Rodolphe Devillers2,3, Marie-Josée Fortin4 1Centre for Fisheries Ecosystems Research, Marine Institute, Memorial University of Newfoundland, St. John’s, Newfoundland and Labrador A1C 5R3, Canada 2Department of Geography, Memorial University of Newfoundland, St. John’s, Newfoundland and Labrador A1B 3X9, Canada 3ARC Centre of Excellence for Coral Reefs Studies, James Cook University, Townsville, Queensland 4811, Australia 4Department of Ecology & Evolutionary Biology, University of Toronto, Ontario M5S 3B2, Canada *Email: matthew.windle@gmail.com ABSTRACT: We examined spatial and temporal relationships between snow crab Chionocetes opilio, shrimp Pandalus spp., Atlantic cod Gadus morhua and the environment (depth, temperature and salinity) on the Newfoundland–Labrador Shelf from 1995 to 2009 using autumn multispecies trawl survey data. First, the core habitat of snow crab and shrimp was determined based on cumulative distribution functions of species abundance over depth and bottom temperature. On average, this method predicted the presence of crab and shrimp at 95 and 99% of trawl locations, respectively, and indicated 90% of crab and shrimp inhabited temperature ranges of −1 to 4 and 0 to 4°C and depths of 100 to 500 and 150 to 450 m, respectively. Then geographically weighted regressions, based on trawl stations where species presence was predicted, indicated spatial non-stationarity between invertebrates and explanatory variables at scales <200 km. Snow crab abundance was best predicted by environmental variables, suggesting bottom-up influences are important, whereas shrimp abundance was influenced by both the environment and cod (predator) abundance. We discuss how averaged ecological relationships within large marine ecosystems central to fisheries management mask processes operating at smaller scales, with reference to the northern cod ecosystem under present conditions of warming waters and increasing cod. KEY WORDS: Spatial ecology · Gadus morhua · Chionoecetes opilio · Pandalus borealis · Northwest Atlantic · Geographically weighted regression · Species interactions Full text in pdf format PreviousNextCite this article as: Windle MJS, Rose GA, Devillers R, Fortin MJ (2012) Spatio-temporal variations in invertebrate−cod−environment relationships on the Newfoundland–Labrador Shelf, 1995−2009. Mar Ecol Prog Ser 469:263-278. https://doi.org/10.3354/meps10026 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 469. Online publication date: November 26, 2012 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2012 Inter-Research.

Effects of temperature and gadid predation on snow crab recruitment: comparisons between the Bering Sea and Atlantic Canada

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 469:249-261 (2012) - DOI: https://doi.org/10.3354/meps09766 Effects of temperature and gadid predation on snow crab recruitment: comparisons between the Bering Sea and Atlantic Canada Laurinda A. Marcello1,*, Franz J. Mueter1, Earl G. Dawe2, Mikio Moriyasu3 1School of Fisheries and Ocean Sciences, University of Alaska Fairbanks, Juneau, Alaska 99801, USA 2Northwest Atlantic Fisheries Centre, Fisheries and Oceans Canada, St John’s, Newfoundland and Labrador A1C 5X1, Canada 3Gulf Fisheries Centre, Fisheries and Oceans Canada, Moncton, New Brunswick E1C 9B6, Canada *Email: laurinda.marcello@gmail.com ABSTRACT: Snow crabs Chionoecetes opilio are found in many subarctic ecosystems, where they are important components of marine food webs and support large commercial fisheries. Snow crab abundance is highly variable, but the causes of large changes in year-class strength are poorly known. We used a regression approach to examine the effects of snow crab spawning stock biomass, bottom water temperature, cold area or sea ice extent, and predation by Pacific cod Gadus macrocephalus or Atlantic cod G. morhua on snow crab recruitment in each of 3 ecosystems: the eastern Bering Sea, the Newfoundland-Labrador Shelf, and the southern Gulf of St. Lawrence. Comparing results across systems showed that cold ocean conditions during early life history were associated with increased snow crab recruitment or recruitment indices in all 3 ecosystems. However, we found no consistent evidence that spawning stock or gadid biomasses were significantly related to subsequent snow crab recruitment. Our results underscore the value of comparing multiple ecosystems and demonstrate the importance of ocean conditions in driving variability in snow crab populations. KEY WORDS: Snow crab · Recruitment · Environment · Predation · Spawning stock biomass · Eastern Bering Sea · Newfoundland-Labrador Shelf · Southern Gulf of St. Lawrence Full text in pdf format PreviousNextCite this article as: Marcello LA, Mueter FJ, Dawe EG, Moriyasu M (2012) Effects of temperature and gadid predation on snow crab recruitment: comparisons between the Bering Sea and Atlantic Canada. Mar Ecol Prog Ser 469:249-261. https://doi.org/10.3354/meps09766 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 469. Online publication date: November 26, 2012 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2012 Inter-Research.