Nekton Diversity Research Articles

Nekton diversity, density, and community structure of spring and autumn in coastal waters of eastern Fujian Province

Nekton diversity, density, and community structure of spring and autumn in coastal waters of eastern Fujian Province

Drifting bryozoans increase nekton diversity in the north- central Gulf of Mexico unvegetated muddy bottom seascape

Bryozoans are sessile suspension-feeders; however, some species become dislodged and represent drifting, ephemeral habitat. Beyond those on drift algae, there are relatively few studies describing the fauna associated with ephemeral habitats and the functions these habitats maintain in estuarine systems. Given the highly structured morphology of bryozoans and the muddy-bottom seascape of the north-central Gulf of Mexico, we hypothesized that the presence of bryozoans in nearshore waters provides additional temporally and spatially ephemeral habitat for invertebrates, small mobile fishes, or early life-stages of estuarine nekton. We examined seine and trawl samples from a long-term fisheries monitoring program operating within Mississippi Sound, Mississippi to test our hypothesis. Overall, we collected 71 and 85 invertebrate taxa in seine (2012–2017) and trawl (2013–2017) samples, respectively, with 40 taxa in common. We also collected 86 and 74 fish taxa overall in all seine (2012–2017) and trawl (2013– 2017) samples, respectively, with 53 taxa in common. We documented highest species richness and species diversity indices when bryozoans were present and in large volumes; however, most of the samples with bryozoans present were collected between September and November. Our results suggest bryozoan mats likely serve as a dispersal mechanism and refugia for estuarine nekton within a soft-sediment seascape as mats pulse shoreward with winds, tides, and currents.

Biodiversity of nekton in the Barumun Watershed, Labuhanbatu District, North Sumatra, Indonesia

Abstract. Dersita, Rambey R, Muhtadi A, Onrizal O, Mamurung VR, Hasibuan JS, Tamba IS. 2022. Biodiversity of nekton in the Barumun Watershed, Labuhanbatu District, Indonesia. Biodiversitas 23: 2426-2432. Biodiversity is a very valuable source of germplasm for science and sustainable development. Therefore, research on freshwater biodiversity is very important to support the sustainability of this development. The research investigated three rivers in South Labuhanbatu District, North Sumatra, Indonesia: Barumun, Tasik, and Titi Kembar rivers. This investigation aims to ascertain the composition, distribution, and variety of nekton. From April to August 2020, the trial lasted five months. Nekton samples were collected with the aid of nets and fishing nets. While installed in the afternoon, the nets are removed the following day. Additionally, at each observation point, stocking nets were operated three times. The investigation discovered 38 fish species and one shrimp species. Two species of fish discovered, are protected by the government of the Republic of Indonesia. Both fish species are Tenualosa terubuk, a fish with little protection, and Fluvitrygon signifer, a ray fish with complete protection. The study site's sole shrimp species was the gigantic prawn Macrobrachium rosenbergii in the Barumun river. The index of nekton diversity discovered in the three rivers was not identical. Compared to other rivers, the Tasik river station has a high diversity. This makes the Tasik river rich in fish compared to the Barumun and Titi Kembar rivers. The Tasik river is recommended as water suitable for fish life from these results.

Ecological equivalency of living shorelines and natural marshes for fish and crustacean communities

Salt marshes provide valued services to coastal communities including nutrient cycling, erosion control, habitat provision for crustaceans and fish (including juvenile and forage fish), and energy transfer from the detrital based food web to the greater estuarine system. Living shorelines are erosion control structures that recreate natural shorelines, such as fringing marshes, while providing other beneficial ecosystem services. Living shorelines are expected to provide fish and crustacean (nekton) habitat, but few comprehensive studies have evaluated nekton habitat use across a range of living shoreline settings and ages. We sampled the intertidal marsh and subtidal shallow water nekton community at 13 paired living shoreline and reference marsh sites, with living shorelines ranging in age from 2 to 16 years from construction. We compared nekton diversity, nekton community abundance, nekton community biomass, forage abundance, and juvenile abundance at reference marshes and living shorelines. Our results indicate that living shorelines are providing suitable marsh habitat for nekton communities, including juveniles and forage base species. The difference in living shoreline construction (rock sill, soil composition) did not appear to diminish habitat quality in the marsh or in nearshore waters, and rock sills may provide enhanced structural shoreline habitat. Living shorelines have the potential to combat marsh habitat loss and provide resilient nekton nursery habitat.

Community structure of nekton in the waters around Dongtou Island in Autumn of 2019

Resource distribution characteristics of nekton in estuarine waters are related to hydrology, ecological environment changes and anthropogenic factors. A total of 49 species of nekton was found from 10 sites in the estuarine waters around Dongtou Island (DTI), with which the species of fish were in the highest proportion, followed by shrimp and crab. Average nekton biomass and abundance were 522.61 kg/km2 and 28.60×103 ind./km2, significantly higher than that of previous studies. The distribution pattern was highest in the eastern part of DTI, lower in the ORE area, and lowest in the northern part of DTI. The intersection of water currents was an important hydrological factor in forming the high resource density area of nekton. Changes in the number of nekton were driven by the contribution of the two economically valuable dominant species of fish Harpodon nehereus and crab Portunus trituberculatus. The mean value of H’ of nekton abundance was higher than that of nekton biomass. The species diversity of nekton in the sea near DTI was relatively low and community structure was in a relatively unstable state. The impact of human development activities on the nekton resources cannot be ignored, further research is essential.

Spatial-seasonal variability of vertebrate assemblages in a Neotropical tidal flat: Recommendations for monitoring the potential impacts of port expansion

Our study aimed to understand the nekton biodiversity of a Neotropical tidal flat in southeastern Brazil (Araçá Bay) and to support its conservation, due to a potential port expansion, by determining: (1) the structure of the local assemblage of nekton (birds, fishes and turtles); (2) its spatial and seasonal variability; (3) potential processes explaining such variability; and (4) the impacts and monitoring measures related to port expansion. Araçá Bay has a high vertebrate richness (205 species, consisting of at least 126 fishes, 78 birds and one turtle species), two invasive fish species, 11 endangered species, a large abundance of target species in fisheries, and a high functional diversity in terms of life history and feeding habits. Mullets, mojarras, sardines and gobies dominate the fish assemblage, while the avifauna is mainly composed of herons and plovers. Green turtles (juveniles) were registered during high tides in all seasons. The low-tide bird and high-tide fish assemblages are spatially structured varying between the inner and the outer area of the flat. In tide pools, fish fauna varies according to bottom type. Juvenile fish predominate; fish assemblage varied according to recruitment and bird’s varied seasonally due to migration. The unique mosaic of habitats and the high productivity of the bay explain the high nekton diversity and make it a locally critical ecosystem for feeding, breeding, and growth. The port expansion would decrease the habitat diversity and productivity in the bay, negatively affecting nekton populations and their ecosystem services. We propose key aspects for nekton monitoring to mitigate port-related impacts.

The effects of intertidal oyster reef habitat characteristics on faunal utilization

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 581:57-70 (2017) - DOI: https://doi.org/10.3354/meps12261 The effects of intertidal oyster reef habitat characteristics on faunal utilization Marc H. Hanke1,2,*, Martin H. Posey1, Troy D. Alphin1 1Department of Biology and Marine Biology, University of North Carolina Wilmington, 601 S. College Road, Wilmington, NC 28403, USA 2Present address: Honors College, University of Houston, 212 MD Anderson Library, 4333 University Dr., Houston, TX 77204-2001, USA *Corresponding author: marc.h.hanke@gmail.com ABSTRACT: The presence, abundance, and distribution of organisms within a landscape are highly dependent on the composition, quality, and configuration of habitat patches. Intertidal oyster Crassostrea virginica reefs provide a structured habitat for many organisms; however, declining oyster populations have induced reef fragmentation and loss. Over 2 years (2011-2012), we evaluated naturally occurring fringing and patch intertidal oyster reefs in southeastern North Carolina, USA, to determine how varied reef type, size, and distance from edge to interior influenced the associated benthic macrofauna and mobile nekton. In addition, the effects of size and edge vs. interior were examined on constructed intertidal reefs at 2 different locations. On the natural reefs, species richness of benthic macrofauna and mobile nekton were significantly increased on fringing reefs. Benthic macrofauna richness significantly decreased on large natural reefs, whereas mobile nekton richness significantly increased off of large reefs. Further, associated benthic macrofauna richness significantly decreased along the reef edge, whereas mobile nekton diversity increased along the reef/open bottom interface. Species richness and densities for benthic macrofauna increased with created reef size, while there was greater species richness and diversity and dissimilar communities for mobile nekton along constructed reef edges. Habitat specificity may influence utilization for mobile nekton, as resident organisms with limited vagility had a stronger response to habitat characteristics. Thus, utilization of intertidal oyster reefs can be highly structured by habitat characteristics on many scales, and should be considered when examining species interactions, ecosystem management, and future restoration efforts. KEY WORDS: Habitat characteristics · Habitat heterogeneity · Patch size · Edge effects · Mobile nekton · Benthic macrofauna · Habitat fragmentation · Habitat restoration · Oyster reefs · Crassostrea virginica Full text in pdf format PreviousNextCite this article as: Hanke MH, Posey MH, Alphin TD (2017) The effects of intertidal oyster reef habitat characteristics on faunal utilization. Mar Ecol Prog Ser 581:57-70. https://doi.org/10.3354/meps12261 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 581. Online publication date: October 13, 2017 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2017 Inter-Research.

Cephalopod biodiversity in the vicinity of Bear Seamount, western North Atlantic based on exploratory trawling from 2000 to 2014

Bear Seamount (BSM) is the most inshore seamount in the New England Seamount chain. It is located within the U.S. Exclusive Economic Zone and is contained within the recently established Northeast Canyons and Seamounts Marine National Monument. In 2000, the National Oceanic and Atmospheric Administration’s (NOAA) National Systematics Laboratory began an exploratory trawling program to document nekton diversity at BSM and its vicinity. Here, we summarize eight exploratory sampling cruises conducted between 2000 and 2014, and describe the cephalopod biodiversity and assemblage structure around BSM. Over the course of 174 deep–midwater and 56 bottom tows, 5088 cephalopods were identified, measured, and documented. In total, 77 species were collected at BSM; 75 species were collected from midwater tows and 28 from benthic tows. Rarefaction curves did not reach an asymptote, suggesting that additional sampling will collect more species. Seventeen species accounted for 75% of the total midwater and bottom catch, including: Illex illecebrosus (n = 605), Magnoteuthis magna (n = 568), Abraliopsis morisii (n = 518), Abralia redfieldi (n = 358), Mastigoteuthis agassizii (n = 336), Histioteuthis reversa (n = 273), Taonius pavo (n = 239), Haliphron atlanticus (n = 195), Brachioteuthis beanii (n = 160), Ornithoteuthis antillarum (n = 153), Pterygioteuthis gemmata (n = 141), Pyroteuthis margaritifera (n = 120), Vampyroteuthis infernalis (n = 101), Chiroteuthis veranyi (n = 33), Bolitaena pygmaea (n = 30), Graneledone verrucosa (n = 11), and Stauroteuthis syrtensis (n = 29). Non-metric multidimensional scaling (NMDS) of significant analysis of similarity (ANOSIM) results showed that the 2000 cruise was different from other years, meteorological winter was different from other seasons, and that day and night shallow samples were different from each other and all other depths. Based on seasonal size variation in the most abundant taxa, we propose hypotheses of year-round, winter, and spring spawning for future critical assessment. This extensive description of the offshore cephalopod assemblage may be used to assess vulnerability to future environmental changes and human activities.

Landscape pattern influences nekton diversity and abundance in seagrass meadows

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 507:139-152 (2014) - DOI: https://doi.org/10.3354/meps10818 Landscape pattern influences nekton diversity and abundance in seagrass meadows Geoffrey M. Hensgen1,*, G. Joan Holt2, Scott A. Holt2, Jason A. Williams3, Gregory W. Stunz3 1Colorado River Alliance, 3625 Lake Austin Boulevard, Austin, TX 78703, USA 2Marine Science Institute, University of Texas at Austin, 750 Channel View Drive, Port Aransas, TX 78373, USA 3Harte Research Institute for Gulf of Mexico Studies, Texas A&M University-Corpus Christi, 6300 Ocean Drive, Corpus Christi, TX 78412, USA *Corresponding author: ghensgen@gmail.com ABSTRACT: We studied how spatial qualities and configuration of seagrass patches influence the diversity and abundance of resident nekton. Shallow landscapes of equal area (4225 m2) in 2 bays were mapped and sampled in the summer and fall to identify different qualities of landscape structure and the abundance and diversity of nekton. Two suites of characteristics were found to describe the natural landscape structure: (1) habitat area, connectivity, patch proximity and patch density; and (2) patch shape complexity and edge length. These were used to quantitatively distinguish between 3 naturally occurring seagrass landscape patterns: (1) small, isolated patches; (2) reticulated edge patches; and (3) continuous cover. Species evenness (Pielou’s J’) was significantly lower in small, isolated patches and reticulated edge patches compared to continuous cover. This pattern was temporally consistent despite significant seasonal differences in total nekton density and seasonal shifts in the distribution of individual species among landscape patterns. Nekton species density (no. of species per 61.2 m2 of seagrass) and species richness (no. of species per 1683 ind. sampled) did not differ significantly among landscape patterns; however, a landscape structure threshold may exist for species evenness between 45 and 85% cover. High densities of shrimp in small, isolated patches and reticulated edge patches during summer drove species evenness levels lower and overall nekton density levels higher than in continuous cover. Large expanses of continuous seagrass harbor more stable nekton communities across time. They may provide enough space for different species to feed and reproduce without depleting food resources to the point that nekton populations become unstable. KEY WORDS: Biodiversity · Seagrass · Landscape structure · Habitat fragmentation Full text in pdf format Supplementary material PreviousNextCite this article as: Hensgen GM, Holt GJ, Holt SA, Williams JA, Stunz GW (2014) Landscape pattern influences nekton diversity and abundance in seagrass meadows. Mar Ecol Prog Ser 507:139-152. https://doi.org/10.3354/meps10818 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 507. Online publication date: July 17, 2014 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2014 Inter-Research.

Spatial Diversity in Composition and Structure of Nekton in Ngenep Spring and its Channels, Karangploso - Malang

Water springs and its channel degradation due to anthropogenic pollution may alter the community structure of aquatic organisms. Water spring degradation tehrefore affect the quality of water as tourism resources. This study aims to investigate the changes in community structure of nekton and determine the relationships between water quality characteristics to the diversity of nekton. The field survey was set up in Ngenep spring and its channels. Results showed that nekton species found in Ngenep spring and its channels consists of 4 classes, 4 orders, 6 families, and 7 species with total 627 nekton samples. It is comprises of fishes, shrimp, frogs and waterstriders. Nekton diversity index (H’) in the spring and irrigation channel were in moderate level (1<H'<3) while in settlement channel was low (0,67). Evenness values of nekton ranged 0,24 – 0,53, whereas dominancy index of nekton ranged 0,41 – 0,74. Evenness value in settlement channel was very low (0, 24) with high dominancy index (0, 74); it indicates that nekton species were spread not evenly in the channel, it dominated by fish Rasbora sp. (highest IVI, 184,95). There were spatial variations of physico-chemical water qualitiy parameters in Ngenep springs and its channels (temperature, stream velocity, turbidity, conductivity, pH, DO, BOD and TOM) which affected to nekton diversity and community structure. Clustering analyses and PCA result shows correlation pattern between nekton distribution with physico-chemical water quality parameters. However, physico-chemical water quality parameters in Ngenep springs and its channel were still optimum as nekton habitat (PP No. 82/ 2001). Keywords: Community structure , Nekton, Spatial diversity, Spring, Water channel

Species composition and community diversity of nekton in Laizhou Bay, China

Based on trawls conducted in Laizhou Bay, China (119°05′–120°00′ E, 37°12′–37°40′ N), in 2010 and 2011, an analysis was made of changes in species composition, dominant species and community diversity of nekton. A total of 85 species were identified, which included 55 fish, 25 crustaceans and 5 cephalopod species. The most species-rich orders were Perciformes (28 species) and Decapoda (24 species). There was obvious seasonal variation in nekton number, mostly influenced by the number of fishes. Sardinella zunasi, Konosirus punctatus and Thryssa kammalensis were the main pelagic fishes in Laizhou Bay, Chaeturichthys stigmatias, Acanthogobius ommaturus and Cynoglossus joyneri were the main bottom fishes, Orgtosaquilla oratoria, Charybdis japonica and Crangon hakodatei were the main crustaceans, while squid (Loliolus sp.) represented the main cephalopods. Loliolus sp., Chaeturichthys stigmatias and Konosirus punctatus were the dominant species in both 2010 and 2011 and the Shannon-Wiener diversity index was highest in summer and lowest in winter. The Shannon-Wiener index was also higher in the north-east area and lower in the south-west. Since the late 538 生 物 多 样 性 Biodiversity Science 第 21卷 1950s, nekton number, especially of fish, has significantly declined due to human activities and climate change impacts. This is particularly true for cartilaginous fish, estuarine species, river-migratory species, large-scale economic fish, flatfish and takifugu. In parallel, dominant species, such as Trichiurus lepturus, Setipinna taty, Engraulis japonicus, Thryssa kammalensis have been replaced by smaller nekton.

DIVERSITY OF NEKTON IN DONGSHAN BAY AND ADJACENT AREAS

The analyses of diversity of nekton in Dongshan Bay and adjacent areas were carried out based on the data of bottom surveys from November 2009 to August 2010.A systematic analysis of the nekton species composition was studied,and the index of relative importance(IRI),relative resource density,Margalef richness index,Shannon-Weiner diversity index and Pielou evenness index were employed to assess the diversity of nekton.Also the spatial-temporal pattern of the nekton species in this area was described.The results showed that there were a total of 168 species involving 20 orders,74 families and 109 genera in Dongshan Bay and adjacent areas.There were 114 fish species which was the largest category,accounting for 67.86%,and the results were shown the same trend compared with that of Taiwan Strait.In term of seasonal distribution,the most abundant of species was in spring(95) and least in autumn(66);in term of the spatial distribution,the survey station 9 in summer had the largest number of nekton species(37),while the survey station 3 had the least number(5) in the spring.The relative resource densities of spring and autumn were the higher,with winter the lowest and summer moderate.Dominant species had relatively less number of species,no more than four species,the number of dominant species in spring,summer,autumn and winter was 4,2,1 and 3 respectively.Dominant species were quite different and there was an obvious seasonal fluctuation.The level of diversity index indicated summer spring autumn winter.In term of the seasonal distribution,the average values of Margalef richness index,Shannon-Weiner diversity index and Pielou evenness index were 3.54,1.99 and 0.71 respectively.In term of the spatial distribution,the average values of Margalef richness index,Shannon-Weiner diversity index and Pielou evenness index were 7.87,2.94 and 0.75 respectively.Biodiversity of nekton in the area was at a low level,which was mainly due to over-fishing,water pollution and other comprehensive factors.This study could provide a scientific basis for marine construction,evaluation of fishery resources,marine ecological restoration,ecosystem-based fisheries and marine management strategy.

Physicochemical conditions and biodiversity in the freshwater fishing area of Pak Phanang River Basin, Thailand

This study was conducted to assess the health of the aquatic environment, particularly its physicochemical variables and the diversity of phytoplankton, zooplankton, macrobenthos and nekton in the freshwater fishing area of the Pak Phanang River Basin (PPRB) of Nakhon Si Thammarat Province, southern Thailand, at three different sites (upstream, midstream and downstream) and seasons (dry, early rainy and heavy rainy seasons), 7 years after dam construction by applying standard methods. Results showed that physicochemical variables changed among sites and seasons, but remained consistent with regulations for inland fisheries of the region. Cluster and multidimensional scaling analyses indicated that the physicochemical variables, macrobenthos and nekton communities primarily changed between study sites, while plankton communities predominantly varied with season. The correlation between physicochemical variables and biotic communities confirmed the relevance of these variables listed in the water quality standard for maintaining aquatic diversity. However, the relevance of some variables (e.g. conductivity, salinity) not listed among the standard variables was also confirmed, which implies that those variables should also be regularly monitored in estuaries like the PPRB. The comparison of nekton diversity figures before and after dam construction revealed a decrease, particularly in brackish and marine species, but, on the other hand, there was an increase among freshwater fish species which was reflected in diversity indices when comparing the most recent indices to those of 2003 (4 years after dam construction). These results indicate an improvement in the biodiversity of freshwater species that was consistent with findings on the suitability of the physicochemical conditions of the freshwater fishing area of the PPRB.

Biodiversity and Ecosystem Function in the Gulf of Maine: Pattern and Role of Zooplankton and Pelagic Nekton

This paper forms part of a broader overview of biodiversity of marine life in the Gulf of Maine area (GoMA), facilitated by the GoMA Census of Marine Life program. It synthesizes current data on species diversity of zooplankton and pelagic nekton, including compilation of observed species and descriptions of seasonal, regional and cross-shelf diversity patterns. Zooplankton diversity in the GoMA is characterized by spatial differences in community composition among the neritic environment, the coastal shelf, and deep offshore waters. Copepod diversity increased with depth on the Scotian Shelf. On the coastal shelf of the western Gulf of Maine, the number of higher-level taxonomic groups declined with distance from shore, reflecting more nearshore meroplankton. Copepod diversity increased in late summer, and interdecadal diversity shifts were observed, including a period of higher diversity in the 1990s. Changes in species diversity were greatest on interannual scales, intermediate on seasonal scales, and smallest across regions, in contrast to abundance patterns, suggesting that zooplankton diversity may be a more sensitive indicator of ecosystem response to inter annual climate variation than zoo plankton abundance. Local factors such as bathymetry, proximity of the coast, and advection probably drive zooplankton and pelagic nekton diversity patterns in the GoMA, while ocean-basin scale diversity patterns probably contribute to the increase in diversity at the Scotian Shelf break, a zone of mixing between the cold-temperate community of the shelf and the warm-water community offshore. Pressing research needs include establishment of a comprehensive system for observing change in zooplankton and pelagic nekton diversity, enhanced observations of "underknown" but important functional components of the ecosystem, population and metapopulation studies, and development of analytical modeling tools to enhance understanding of diversity patterns and drivers. Ultimately, sustained observations and modeling analysis of biodiversity must be effectively communicated to managers and incorporated into ecosystem approaches for management of GoMA living marine resources.

Small-scale distribution of deep-sea demersal nekton and other megafauna in the Charlie-Gibbs Fracture Zone of the Mid-Atlantic Ridge

Abstract Videotapes from manned submersibles diving in the area of the Charlie-Gibbs Fracture Zone of the Mid-Atlantic Ridge were used to investigate the distribution of fishes, large crustaceans, epifaunal and sessile organisms, and environmental features along a series of transects. Submersibles MIR 1 and MIR 2 conducted paired dives in an area of mixed sediment and rock (beginning depth ca. 3000 m) and on a large pocket of abyssal-like sediments (depth ca. 4000 m). In the shallower area, the submersibles passed over extremely heterogeneous terrain with a diversity of nekton, epifaunal forms and sessile forms. In the first pair of dives, MIR 1 rose along the Mid-Atlantic Ridge from 3000 to 1700 m, while MIR 2 remained near the 3000 m isobath. Nekton seen in these relatively shallow dives included large and small macrourids (genus Coryphaenoides ), shrimp (infraorder Penaeidea), Halosauropsis macrochir , Aldrovandia sp., Antimora rostrata , and alepocephalids. The last two were more characteristic of the upper areas of the slope reached by MIR 1, as it rose along the Mid-Atlantic Ridge to depths less than 3000 m. Distributions of some forms seemed associated with depth and/or the presence of hard substrate. Sessile organisms such as sponges and large cnidaria were more likely to be found in rocky areas. The second pair of dives occurred in an abyssal area and the submersibles passed over sediment-covered plains, with little relief and many fewer countable organisms and features. The most evident of these were holes, mounds, small cerianthid anemones, small macrourids and the holothurian Benthodytes sp. A few large macrourids and shrimp also were seen in these deeper dives, as well as squat lobsters ( Munidopsis sp.). Sponges and larger cnidaria were mostly associated with a few small areas of rocky substrate. Holes and mounds showed distributions suggesting large-scale patterning. Over all dives, most sessile and epifaunal forms showed clumped distributions. However, large holothurians and large nekton often had distributions not significantly different from random.

The impact of marine reserves on nekton diversity and community composition in subtropical eastern Australia

The effectiveness of marine reserve protection on the biodiversity of aquatic assemblages (i.e. nekton) in subtropical eastern Australia was examined within two small (<6 km 2) marine reserves and four non-reserve areas. The two marine reserves, and their corresponding non-reserves, were located in different geographical locations within Moreton Bay (north and south) and sites were surveyed with multiple hauls of a seine net. Species richness, evenness, density and mean size of the inshore communities were compared between the reserves and non-reserves. No statistical significant difference was detected in species richness between the areas however species evenness was significantly lower in the only non-reserve site impacted by commercial net fishing. Mean size of nekton was found to be significantly greater in the marine reserves compared to non-reserves but no statistical significant difference was found in the density of nekton between the study sites. Multivariate analysis revealed differences in community composition, particularly between the geographical locations where areas were impacted by different types of fishing pressure (recreational v commercial). These results highlight the impact commercial fishing can have on entire nekton assemblages, not just on targeted species. Our study demonstrates that the small marine reserves in Moreton Bay are protecting marine biodiversity and are thus at least partially achieving their management objective (to enhance the zone’s marine biodiversity).

Nekton habitat quality at shallow water sites in two Rhode Island coastal systems

We evaluated nekton habitat quality at 5 shallow-water sites in 2 Rhode Island systems by comparing nekton densities and biomass, number of species, prey availability and feeding, and abundance of winter flounderPseudopleuronectes americanus. Nekton density and biomass were compared with a 1.75-m2 drop ring at 3 sites (marsh, intertidal, and subtidal) in Coggeshall Cove in Narragansett Bay and two subtidal sites (eelgrass and macroalgae) in Ninigret Pond, a coastal lagoon. We collected benthic core samples and examined nekton stomach contents in Coggeshall Cove. We identified 16 species of fish, 16 species of crabs, and 3 species of shrimp in our drop ring samples. A multivariate analysis of variance indicated differences in total nekton, invertebrates, fish, and winter flounder across the five sites. Relative abundance of benthic invertebrate taxa did not match relative abundance of prey taxa identified in the stomachs. Nonmetric multidimensional scaling plots showed groupings in nekton and benthic invertebrate prey assemblages among subtidal, intertidal, and marsh sites in Coggeshall Cove. Stepwise multiple regression indicated that biomass of macroalgae was the most important variable predicting abundance of nekton in Coggeshall Cove, followed by elevation and depth. In Rhode Island systems that do not experience chronic hypoxia, macroalgae adds structure to unvegetated areas and provides refuge for small nekton. All sites sampled were characterized by high abundance and diversity of nekton pointing to the importance of shallow inshore areas for production of fishes and decapods. Measurements of habitat quality should include assessment of the functional significance of a habitat (this can be done by comparing nekton numbers and biomass), some measure of habitat diversity, and a consideration of how habitat quality varies in time and space.