Small-scale Distribution Patterns Research Articles

Predator-prey interactions in a coastal setting: Linking crab feeding rates to small scale distribution of clams

A coastal predator-prey system, juvenile green crabs (Carcinus maenas) preying upon juvenile hard clams (Mercenaria mercenaria), was used to explore the link between crab predation rates and clam density and small-scale distribution patterns. The channel working area of a racetrack flume was adapted to form a sedimentary arena in a flowing seawater system (5 cm s−1) to assess crab predation rates in relation to clam density and distribution patterns (clams clustered in one patch vs two nearby vs two farther apart). The trials detected significant differences in relation to clam initial density and distribution with strong (∼50%) declines in clam mortality levels among spatial arrangements (one patch > two nearby > two farther apart). Feeding of clams was associated with the time taken by crabs to handle the first clam (first patch), and the frequency of three distinct types of crab behavior (eating, resting, and searching). Altogether these results suggest that small-scale changes in number and distribution of juvenile clams matter and may have unexpectedly strong effects on the outcome of predator-prey interactions.

Small-scale spatial distribution of ghost shrimp and macrobenthic fauna in an Amazon macrotidal dissipative sandy beach

ABSTRACT Spatial changes in environmental characteristics strongly influence the structure of benthic communities on sandy beaches, where the patterns of occurrence are mainly controlled by morphodynamic characters and biological interactions. Despite being very abundant and extensive, the Amazonian sandy beaches are among the coastal environments less well known to science. On these beaches, the ghost shrimp Lepidophthalmus siriboia Felder and Rodrigues, 1993 is an important component of the intertidal macrofauna. The present study describes the small-scale distribution patterns of L. siriboia and of the macrobenthic communities in a dissipative macrotidal Amazonian sandy beach. Samples were collected in the intertidal zone of two areas: Area 1, next to a tidal channel; and Area 2, away from the tidal channel. In Area 1, with finer sediments, there was a higher burrow density of L. siriboia and higher density and species richness of macrofauna. In both areas, the burrow density of L. siriboia increased towards the sea. The faunal distribution patterns can be explained by changes in flooding and the type of substratum across the shore and alongshore. These findings add to our knowledge of tropical sandy beach ecology and reinforce the idea that tropical macrotidal beaches have a complexity of morphological features, which are drivers of macrofaunal structure.

Classical and computed tomographic anatomical analyses in a not-so-cryptic Alviniconcha species complex from hydrothermal vents in the SW Pacific

The chemosymbiotic gastropod Alviniconcha (Provannidae), first described in 1988, is one of the most emblematic hydrothermal-vent taxa described from the Central Indian Ridge and the Southwest (SW) Pacific. Symbiotic bacteria found in the gill of Alviniconcha are thought to be their principal source of nutrition. In the SW Pacific, species distributions for A. kojimai, A. boucheti – and to a lesser extent A. strummeri – overlap. While Alviniconcha species do not appear to truly co-exist in these highly energetic but spatially limited habitats, certain species regularly co-occur within a single vent field and in rare instances, the same edifice. Past research suggests that SW-Pacific Alviniconcha species might aggregate around fluids with distinct geothermal profiles. These small-scale distribution patterns have been attributed to differences in their symbiont assemblages or host physiologies. However, little is known about the anatomy of most Alviniconcha species, beyond that detailed for the type species Alviniconcha hessleri, whose geographic range does not overlap with other congeners. In fact, species within this genus are currently described as cryptic, despite the absence of any comparative morphological studies to assess this. To test whether the genus is genuinely cryptic and identify any functional differences in host anatomy that might also mediate habitat partitioning in SW Pacific species, the current study examined the morphoanatomy of A. kojimai, A. boucheti and A. strummeri from the Fatu Kapa vent field, an area of hydrothermal activity recently discovered north of the Lau Basin near the Wallis and Futuna Islands and the only known example where all three species occur within adjacent vent fields. A combination of detailed dissections, histology and X-ray computed tomography demonstrate that A. kojimai, A. strummeri and A. boucheti are readily identifiable based on shell morphology and ornamentation alone, and therefore not truly cryptic. These traits provide a rapid and reliable means for species identification. However, aside from some subtle differences in radular morphology, these species of Alviniconcha exhibit conserved anatomical features, providing no evidence that functional host anatomy is implicated in habitat partitioning. This provides support for the current belief that host-species distributions are probably governed by symbiont-mediated physiological factors.

Linking large-scale and small-scale distribution patterns of steppe plant species—An example using fourth-corner analysis

The Mongolian share of the Palaearctic steppe biome hosts some of most intact grassland regions, these are traversed by high peaks creating diverse and rich habitats. We sampled 100 randomly located vegetation plots in a 2 × 2 km² mountain summit region that is isolated by surrounding drier lowlands in the Gobi Gurvan Saykhan mountain range in southern Mongolia. All sampled plants were assigned to phytogeographic groups using new data on their geographic distribution ranges. Relationships between local scale and global scale distribution were analysed with fourth-corner analysis. To this end, we investigated if statistical methods developed for functional trait analysis can be used in a biogeographical context to test whether plot-level vegetation patterns mirror range-level distribution data. Furthermore, we determined if range distributions are reflected in habitat preferences, and how this link could be applied to decision-making in conservation biology. The fourth-corner analysis revealed that phytogeographical groups showed significant preferences for certain local habitat types in the heterogeneous mountain range. The local, Central Asian endemics showed, however, no clear preference along the altitudinal gradient. Fourth-corner analysis proofed useful for testing relations between local scale habitat preferences and large-scale distribution. In the Gobi Altay, species at their distribution limits where much more strongly restricted in their local distribution, while endemics tended to cover a wider range of local habitat conditions. Given that biogeographical responsibility has become a major topic in conservation biology, the approach can also be helpful for applied studies elsewhere.

Ecology and distribution ofDermatocarpon(Verrucariaceae,Ascomycota) in the catchment areas of two Bulgarian rivers

AbstractTemperature preferences and small-scale distribution patterns of fourDermatocarpontaxa in the catchment areas of two Bulgarian rivers were analyzed. Taxa with an overall alpine or arctic-alpine distribution were restricted to microhabitats with the lowest water and rock surface temperatures. A trend for increasingDermatocarpon rivulorumthallus diameter and colony size (aggregates of thalli) with decreasing temperature was identified. Data on pH and conductivity of the water for the study sites are provided for all taxa.Dermatocarpon arnoldianumis reported for the first time from Bulgaria, confirmed by ITS sequence data, and its known range extends to South-East Europe. All previous records ofD. rivulorumfrom Bulgaria were based on misidentified specimens ofD. arnoldianum. Freshwater taxa ofDermatocarponare proposed as a tool for monitoring the biological effects of temperature changes due to global climate change. Thallus and colony size are recommended as additional features for monitoring populations of threatenedDermatocarponspecies.

Influence of a narrow depth gradient on the spatial structure of Sargassum peracarid assemblages in Southeastern Brazil

A depth gradient may influence both macrophytes and their associated epiphytic community through variations in hydrodynamics and light conditions, which in turn may affect the mobile organisms living on them. We investigated how a narrow depth gradient affects the associated peracarid assemblages in a Sargassum cymosum bed. This study was conducted on a rocky shore in Southeastern Brazil. A 20 × 3 m sampling area was defined parallel to the shore line, within which three perpendicular transects were sampled in October 1997 (spring), January 1998 (summer), April 1998 (fall), and July 1998 (winter). In each transect, three samples of Sargassum were randomly collected at three different depths—shallow (1 m), intermediate (2 m), and deep (3 m). Peracarid fauna was identified, quantified, and classified into feeding groups. Depth affected both species richness and total density only in January, with fewer species and individuals at the shallow depth, more species at the intermediate depth, and more individuals at the deep depth. The taxonomic and feeding group composition of peracarid assemblages were also affected by depth, with differences depending on the sampling period. Herbivores and omnivores were commonly more abundant at the shallow depth, while detritivores were more abundant at the deep depth. Carnivores seemed not to be affected by depth. Small-scale distribution patterns can be related to how peracarid species deal with the variability in turbulence and food availability imposed by a depth gradient, with morphological attributes and feeding habits guiding how species are distributed in the space and thus the peracarid assemblage as a whole.

Low abundance and high species richness: the structure of the soft-bottom isopod fauna of a West Antarctic glacial fjord

Isopods belong to the most speciose groups of the Antarctic benthic fauna, although the knowledge on their diversity and small-scale distribution patterns is still limited. Here we analyze the diversity of the isopod fauna in the Admiralty Bay, a glacial fjord on the King George Island. The basin is located in the region of the Antarctic Peninsula, the fastest warming area of the Southern Ocean. The study provides important baseline data for future research, particularly with respect to temporal fluctuations in benthic fauna, associated with global changes observed in that part of the world. Forty species of isopods representing 19 families were recorded on the soft bottom of the Admiralty Bay. The analyses were based on 99 quantitative samples collected, within the 20–502-m depth range, with a 0.1 m2 van Veen grab. The materials for the analyses were obtained in the austral summer seasons of 1984/1985 and 1985/1986. The data revealed a high number of isopod species occurring at a low abundance, the mean abundance amounting to 4.8 ± 8.6 ind./0.1 m2. Most of the species occurred at low abundances, 25% of the species being represented by singletons. Caecognathia polaris, the most abundant species, showed the mean abundance of merely 1.2 ± 4.2 ind./0.1 m2. Species richness, diversity and abundance of the isopod fauna were much higher in the central basin of the Admiralty Bay than in the Ezcurra Inlet, an area affected by a strong disturbance of glacial origin.

Exposure to solar radiation drives organismal vulnerability to climate: Evidence from an intertidal limpet

Understanding the physiological abilities of organisms to cope with heat stress is critical for predictions of species’ distributions in response to climate change. We investigated physiological responses (respiration and heart beat rate) of the ectotherm limpet Patella vulgata to heat stress events during emersion and the role of seasonal and microclimatic acclimatization for individual thermal tolerance limits. Individuals were collected from 5 microhabitats characterized by different exposure to solar radiation in the high intertidal zone of a semi-exposed rocky shore in winter and summer of 2014. Upper thermal tolerance limits (heat coma temperatures – HCTs, and heart rate Arrhenius break temperatures - ABTs) were determined for individuals from each microhabitat in both seasons under laboratory conditions. While we found a clear seasonal acclimatization, i.e., higher HCTs and ABTs in summer than in winter, we did not find evidence for microhabitat-specific responses that would suggest microclimatic acclimatization. However, operative limpet temperatures derived from in-situ temperature measurements suggest that individuals from sun exposed microhabitats have a much narrower thermal safety margins than those from less exposed surfaces or within crevices. Microhabitat specific thermal safety margins caused by high thermal heterogeneity at small spatial scales and the lack of short term acclimatization will likely shape small scale distribution patterns of intertidal species in response to the predicted increase in the frequency and intensity of heat waves.

Coastal Fronts Utilized by Migrating Humpback Whales, Megaptera novaeangliae, on the Gold Coast, Australia

ABSTRACT Reinke, J.; Lemckert, C., and Meynecke, J.-O., 2016. Coastal fronts utilised by migrating humpback whales, Megaptera novaeangliae, on the Gold Coast, Australia. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 552–556. Coconut Creek (Florida), ISSN 0749-0208. Large-scale migration patterns of humpback whales, Megaptera novaeangliae, are quite well known; however, small-scale distribution patterns and relationships with environmental conditions have received less attention. Protection from a range of threats, as well as predicting the effects of climate change, requires knowledge of preferred habitat and environmental conditions. East Australian humpback whales travel from the Southern Ocean towards the Great Barrier Reef to breed. The East Australian coastal environment is dominated by the East Australian Current that carries warm water po...

Spatial distribution patterns and movements of Holothuria arguinensis in the Ria Formosa (Portugal)

Holothurian populations are under pressure worldwide because of increasing demand for beche-de-mer, mainly for Asian consumption. Importations to this area from new temperate fishing grounds provide economic opportunities but also raise concerns regarding future over-exploitation. Studies on the habitat preferences and movements of sea cucumbers are important for the management of sea cucumber stocks and sizing of no-take zones, but information on the ecology and behavior of temperate sea cucumbers is scarce. This study describes the small-scale distribution and movement patterns of Holothuria arguinensis in the intertidal zone of the Ria Formosa national park (Portugal). Mark/recapture studies were performed to record their movements over time on different habitats (sand and seagrass). H. arguinensis preferred seagrass habitats and did not show a size or life stage-related spatial segregation. Its density was 563ind.ha−1 and mean movement speed was 10m per day. Movement speed did not differ between habitats and the direction of movement was offshore during the day and shoreward during the night. Median home range size was 35m2 and overlap among home ranges was 84%. H. arguinensis' high abundance, close association with seagrass and easy catchability in the intertidal zone, indicate the importance of including intertidal lagoons in future studies on temperate sea cucumber ecology since those systems might require different management strategies than fully submerged habitats.

Microclimatic differentiation of gene pools in the Lobaria pulmonaria symbiosis in a primeval forest landscape.

Population genetics of the tree-colonizing lichen Lobaria pulmonaria were studied in the largest primeval beech forest of Europe, covering 10000ha. During an intensive survey of the area, we collected 1522 thallus fragments originating from 483 trees, which were genotyped with eight mycobiont- and 14 photobiont-specific microsatellite markers. The mycobiont and photobiont of L.pulmonaria were found to consist of two distinct gene pools, which are co-existing within small areas of 3-180ha in a homogeneous beech forest. The small-scale distribution pattern of the symbiotic gene pools show habitat partitioning of lineages associated with either floodplains or mountain forests. Using approximate Bayesian computation (ABC), we dated the divergence of the two fungal gene pools of L.pulmonaria as the Early Pleistocene. Both fungal gene pools survived the Pleistocene glacial cycles in the Carpathians, although possibly in climatically different refugia. Fungal diversification prior to these cycles and the selection of photobionts with different altitudinal distributions explain the current sympatric, but ecologically differentiated habitat partitioning of L.pulmonaria. In addition, the habitat preferences of the mycobiont are determined by other factors and are rather independent of those of the photobiont at the landscape level. The distinct gene pools should be considered evolutionarily significant units and deserve specific conservation priorities in the future, for example gene pool A, which is a Pliocene relict.

Living where others dare not: Microhabitat distribution in Chorizanthe rigida, a serotinous desert annual

We studied the small scale distribution pattern of Chorizanthe rigida, a serotinous desert annual, in a shrub-mound-to-desert-pavement gradient. Two sites were established in the Mojave Desert and two sites where established in the Sonoran Desert. We placed transects along a soil surface gradient from shrub mounds to desert pavements, and measured land surface properties, soil characteristics, and C. rigida's small scale distribution. A Principal Components Analysis was done on the resulting site × soil variables matrix. C. rigida established preferentially in desert pavements outside shrub canopies. Pavements showed finer soil textures and higher electrical conductivities, while shrub mounds had sandy textures, low surface rockiness, higher nitrogen, and higher cover of annuals. We discuss a probable relationship between seed retention and the establishment on desert pavements: timing seed release allows this species to avoid wind- or animal-induced seed dispersal into shrub mounds and establish outside the nurse mounds, where most annual plants concentrate. The seeds encased in the serotinous involucres, released after rains, are dispersed by run-off into the desert pavements and transition zones where, once developed, the dead seed-retaining structures of adult C. rigida plants persist for years releasing seeds to subsequent rain events.

Small-scale distribution patterns of two cirratulid species with a description of a peculiar early juvenile stage

An assemblage of cirratulids in a confined marine basin (Mediterranean Sea) was investigated at small spatio-temporal scales in an experiment in which artificial granules of expanded fire-clay were used as a bare substratum for colonization. Analysis of core samples of 3.5 l undisturbed natural sediments (source area) and equal volumes of artificial substratum (new settlement area), plunged into the sea bottom were carried out from May to July 2008 after 0, 15, 30 and 60 days.Caulleriella bioculatashowed the highest total mean density of 10.1 ± 5.8 N l−1in the natural sediment, and the lowest at 0.13 ± 0.08 N l−1in the artificial substratum, with a marked temporal decrease. Individuals were not strongly aggregated and were found in a deeper sediment layer. The density of largeCirriformia tentaculatawas 0.5 ± 0.3 N l−1, with individuals more aggregated and confined to shallower sediments, versus 0.10 ± 0.06 N l−1but found deeper in the artificial substratum; temporal trends were not straightforward for this species. The adult stage of sedentary cirratulids appeared to actively move into the new available substratum from the neighbouring sediments. An early cirratulid juvenile stage was observed in both microhabitats at a comparable density of 1.8 ± 2.8 N l−1with highly aggregated individuals (cohorts). The peculiar morphology of branchiae, the threadlike body shape and the multivariate morphological differences between two sub-populations settled in the different substrata are reported for these problematic specimens.

Active moss biomonitoring of small-scale spatial distribution of airborne major and trace elements in the Belgrade urban area

In urban environments, human exposure to air pollutants is expected to be significantly increased, especially near busy traffic streets, street canyons, tunnels, etc. where urban topography and microclimate may additionally cause poor air conditions giving rise to pollution hotspots. As a practical and cost-effective approach, active moss biomonitoring survey of some major and trace element air pollution was performed in the Belgrade street canyons and city tunnel in 2011 with the aim to evaluate possibility of using Sphagnum girgensohnii moss bags for investigation of the small-scale vertical and horizontal distribution patterns of the elements. In five street canyons, the moss bags were hung at heights of about 4, 8 and 16 m, during 10 weeks, and also, for the same time, the moss bags were exposed in the tunnel, in front of and out of it. After the exposure period, the concentrations of Al, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Sr, V and Zn in the moss were determined by inductively coupled plasma optical emission spectrometry. According to the results, in all street canyons, the vertical distribution patterns of the moss elements concentration (Al, Ba, Co, Cr, Cu, Ni, Pb, Sr, V and Zn) showed statistically significant decrease from the first to the third heights of bags exposure. In the tunnel experiment, from inner to out of the tunnel, for Al, Ba, Cd, Co, Cr, Cu, Fe, K and Zn, decreasing trend of concentrations was obtained. Significantly higher concentration of the elements was pronounced for the tunnel in comparison with the street canyons. The results indicate that the use of S. girgensohnii moss bags is a simple, sensitive and inexpensive way to monitor the small-scale inner city spatial distribution of airborne major and trace element content.

Small-Scale Heterogeneity in Deep-Sea Nematode Communities around Biogenic Structures

The unexpected high species richness of deep-sea sediments gives rise to the questions, which processes produce and maintain diversity in the deep sea, and at what spatial scales do these processes operate? The idea of a small-scale habitat structure at the deep-sea floor provides the background for this study. At small scales biogenic structures create a heterogeneous environment that influences the structure of the surrounding communities and the dynamics of the meiobenthic populations. As an example for biogenic structures, small deep-sea sponges (Tentorium semisuberites Schmidt 1870) and their sedimentary environment were investigated for small-scale distribution patterns of benthic deep-sea nematodes. Sampling was carried out with the remotely operated vehicle Victor 6000 at the Arctic deep-sea observatory HAUSGARTEN. In order to investigate nematode community patterns sediment cores around three small sponges and corresponding control cores were analysed. A total of approx. 5800 nematodes were identified. The comparison of the nematode communities from sponge and control samples indicated an influence of the biogenic structure “sponge” on diversity patterns and habitat heterogeneity. The increased number of nematode species and functional groups found in the sediments around the sponges suggest that on a small scale the sponge acts as a gradient and creates a more divers habitat structure. The nematode community from the sponge sediments shows a greater taxonomic variance and species richness together with lower relative abundances of the species compared to those from control sediments. Obviously, the more homogeneous habitat conditions of the control sediments offer less micro-habitats than the sediments around the sponges. This seems to reduce the number of functional groups and species coexisting in the control sediments.

Landscape of fear influences the relative importance of consumptive and nonconsumptive predator effects

Predators can initiate trophic cascades by consuming and/or scaring their prey. Although both forms of predator effect can increase the overall abundance of prey's resources, nonconsumptive effects may be more important to the spatial and temporal distribution of resources because predation risk often determines where and when prey choose to forage. Our experiment characterized temporal and spatial variation in the strength of consumptive and nonconsumptive predator effects in a rocky intertidal food chain consisting of the predatory green crab (Carcinus maenas), an intermediate consumer (the dogwhelk, Nucella lapillus), and barnacles (Semibalanus balanoides) as a resource. We tracked the survival of individual barnacles through time to map the strength of predator effects in experimental communities. These maps revealed striking spatiotemporal patterns in Nucella foraging behavior in response to each predator effect. However, only the nonconsumptive effect of green crabs produced strong spatial patterns in barnacle survivorship. Predation risk may play a pivotal role in determining the small-scale distribution patterns of this important rocky intertidal foundation species. We suggest that the effects of predation risk on individual foraging behavior may scale up to shape community structure and dynamics at a landscape level.

Symbiosis of sea anemones and hermit crabs: different resource utilization patterns in the Aegean Sea

The small-scale distribution and resource utilization patterns of hermit crabs living in symbiosis with sea anemones were investigated in the Aegean Sea. Four hermit crab species, occupying shells of nine gastropod species, were found in symbiosis with the sea anemone Calliactis parasitica. Shell resource utilization patterns varied among hermit crabs, with Dardanus species utilizing a wide variety of shells. The size structure of hermit crab populations also affected shell resource utilization, with small-sized individuals inhabiting a larger variety of shells. Sea anemone utilization patterns varied both among hermit crab species and among residence shells, with larger crabs and shells hosting an increased abundance and biomass of C. parasitica. The examined biometric relationships suggested that small-sized crabs carry, proportionally to their weight, heavier shells and increased anemone biomass than larger ones. Exceptions to the above patterns are related either to local resource availability or to other environmental factors.

Short-term size-specific distribution and movement patterns of juvenile flatfish in a Pacific estuary derived through length-frequency and mark-recapture data

Evaluating small-scale distribution and movement patterns of juvenile fishes within estuarine systems is necessary for identifying favorable nursery habitats and adequately interpreting local instantaneous growth and mortality estimates. Finescale, size-specific catch per unit effort (CPUE, catch per 500 m tow) and movement of juvenile flatfish were studied in Punta Banda Estuary, Baja California, Mexico, during the summer of 2004. After dividing the estuary into five contiguous sections, habitat utilization and movement were analyzed using two complimentary approaches. We intensively surveyed the estuary throughout the summer to document the size-specific distribution of flatfishes. California halibut and diamond turbot were captured throughout the estuary on all sampling dates, indicating that the entire system serves as habitat for juveniles. Multiple regression analysis indicated that the CPUE of California halibut was significantly and negatively related to temperature and depth, although the model exhibited low explanatory power. In contrast, the CPUE of diamond turbot was only significantly and negatively related to depth. CPUE was not related to salinity for either species. Analyses of site- and time-specific lengthfrequency distributions indicated movement by all flatfishes on the time scale of weeks, which is likely due to the estuarine emigration of fish >140 mm standard length. In addition, an estuary-wide mark-recapture study was performed. Visible elastomer implants were used to tag 697 California halibut, 442 diamond turbot, and 128 spotted turbot. Based on sectionspecific CPUE and the area of the estuary, we tagged 3–6% of the local population of each species in a given month. Four Californian halibut and two diamond turbot were recaptured within hundreds of meters of where they were released. Hence, we observed residency and movement at the same time. This study indicates that short-term movement and its underlying causes should be taken into account when assessing patterns of juvenile habitat utilization.

Habitat features affecting the small-scale distribution and longitudinal migration patterns of Calotriton asper in a Pre-Pyrenean population

AbstractThe longitudinal movements and abiotic factors that determine the distribution of Pyrenean mountain newts (males, females, amplexus and metamorphic newts) were examined in a 1500 meters segment of a Pre-Pyrenean stream. Migration of adult newts was studied by means of capture-recapture techniques in the course of one year. Our results indicate that the mean distance the newts migrated per year was less than 50 meters and the population could be considered sedentary. No significant differences in longitudinal movement patterns between the sexes were observed, and movement patterns were more or less constant over time. Habitat variables determining newt abundance was estimated by means of a GLM. Our results indicate that the number of refugia (wood debris, stones and fissures) determines the distribution of newts. Larval abundance was correlated with stream-bed structure.

Population and Production Estimates for Decapod Crustaceans in Wetlands of Galveston Bay, Texas

Abstract The value of wetlands is reflected in the relative abundance and production of nekton, but these population variables have been difficult to estimate because of sampling problems, landscape complexity, tidal dynamics, and limited information on growth and mortality. We combined a landscape analysis of land-water patterns in regularly flooded wetlands of lower Galveston Bay, Texas, with data on small-scale (1-50-m) distribution patterns of nekton over the marsh surface to estimate population abundances of juvenile brown shrimp Farfantepenaeus aztecus, white shrimp Litopenaeus setiferus, and blue crab Callinectes sapidus. Using information on size frequencies, size-weight relationships, and growth rates, we estimated the wet biomass and production of these species from salt marshes and open-water habitats. In 17,673 ha of marsh complex (vegetation with a 150-m water buffer) in lower Galveston Bay, we estimated the standing crops (number/ha) at 19,382 for brown shrimp, 17,406 for white shrimp, and 1...