Estuarine Fauna Research Articles

The AD 1755 tsunami deposits onshore and offshore of Algarve (south Portugal): Sediment transport interpretations based on the study of Foraminifera assemblages

Tsunamis are amongst the most catastrophic natural hazards affecting worldwide coastal areas. Their impacts are recorded in the geological archives and its study provides crucial insights into the dynamics and intensity of these events. The accurate establishment of return periods can also be derived using sedimentological data. Onshore tsunami deposits have been extensively described over recent years through the application of a wide range of sedimentological proxies, including micropalaeontological analysis.In this work, the identification of palaeotsunami evidence, in both the onshore and offshore sedimentary record of south Portugal, was performed, relying mostly on the study of Foraminifera assemblages. Three onshore trenches and one offshore core were analyzed and imprints of the AD 1755 tsunami were observed based in the identification of allochthonous foraminiferal species, increase in the number of broken/abraded tests and its correlation with coarser mean grain size. This was possible after micropalaeontological environmental characterization of both low-energy onshore and offshore present-day sedimentation regimes.In the onshore record, three distinct sediment transport phases were differentiated within the tsunamigenic unit. The basal phase portraying the initial inundation represented by the dominance of marine Foraminifera species in a highly diverse assemblage. The higher energetic character of this phase was also reflected in the identification of the highest number of broken/abraded tests. The intermediate phase reflects an unspecified number of inundation and backwash pulses that were recognized based in the well-balanced presence of estuarine (brackish) and marine species, the sharp decrease in the diversity index and in the number of broken/abraded tests. The final phase recorded in the tsunamigenic unit registers the imprint of the last relevant backwash which was identified based on the dominance of estuarine (brackish) fauna. The overlying unit is dominated by tidal marsh species, demonstrating the start of the coastal system recovery phase.In the offshore record, it was possible to identify 2 distinct historical tsunami events (AD 1755 and AD 1969). This was achieved through the identification of significant increases in coastal Foraminifera species coupled with the presence of coarser layers. This interpretation was sustained by indirect age-estimation methods (radiocarbon and 210Pb) that ascribed compatible ages to the historical tsunami events. The results obtained in this study stress the relevance and innovative character of this onshore and offshore multiproxy approach in the recognition and understanding of tsunami events.

Relationship Between Estuarine Shellfish Fauna and Physical Environmental Characteristics for Estuary Conservation in Kyushu, Japan

The establishment of a conservation strategy or restoration goal for river estuaries requires knowledge of potential biota or possible habitat characteristics. In this study, we investigated the relationship between estuarine fauna and macro scale physical indicators on Kyushu Island, Japan to provide basic information for estuarine conservation. As a result of the classification of shellfish fauna by similarity, the Kyushu region was divided into three groups, namely, 1) southern Kyushu with high wave exposure, long fetch, and low tidal variation; 2) the Ariake and Yatsushiro seas with low wave exposure, short fetch, and high tidal variation; and 3) northern Kyushu with an intermediate fetch and tidal variation. In addition, a number of sites, such as Nakatsu Port, Sone tideland, and the Honmyou River, were classified into geographically different groups. This is because the physical characteristics of these sites were similar to classified groups or shellfish fauna were significantly altered by artificial impacts. As a result of discriminant analysis, the discrimination hit rate of species inhabiting the inner bay or tidal flat was high, whereas that for species using a wide variety of bottom sediment environment was low. To improve the accuracy of the discriminant model, it is necessary to collect more detailed physical information, such as habitat type, salinity concentration, or grain diameter of bottom sediment. To establish a conservation or restoration strategy, there is a need for classifying taxonomic groups or physical characteristics.

In vitro screening for endocrine disruptive activity in selected South African harbours and river mouths

Various waterborne anthropogenic contaminants disrupt the endocrine systems of wildlife and humans, targeting reproductive pathways, among others. Very little is known, however, regarding the occurrence of endocrine disruptive activity in South African freshwater ecosystems, and coastal ecosystems have not been studied in this regard. In a first attempt to investigate endocrine disruptive activity in South African coastal waters, surface water samples collected from harbours, river mouths and estuaries in three metropolitan municipalities, eThekwini (which includes Durban), Nelson Mandela (specifically Port Elizabeth Harbour) and City of Cape Town, were screened for (anti) oestrogenicity and (anti)androgenicity using recombinant yeast bioassays. Moreover, levels of the female hormone 17β-(o)estradiol (E2) were determined in all samples, as well as a selection of hydrocarbons in the eThekwini samples. A high proportion of samples collected from eThekwini were oestrogenic, whereas none from Port Elizabeth Harbour and only a single river mouth sampled in the City of Cape Town were oestrogenic. E2 was detected in all the samples tested, but at higher concentrations at the eThekwini and City of Cape Town localities than Port Elizabeth Harbour. In addition, the recombinant yeast assays revealed that anti-androgenicity was widespread, being detected in the majority of samples screened apart from those representing Port Elizabeth Harbour. Conversely, no anti-oestrogenic or androgenic activity was detected. Anti-androgenicity did not associate with hydrocarbon loads, providing evidence that other anti-androgens were responsible for the observed activity. The present data suggest potential reproductive disruption in marine and estuarine fauna inhabiting the eThekwini and City of Cape Town regions.

Estuarine Mysids in Sri Lanka: Implications for Conservation

Mysids are important fauna in estuarine hyperbenthic communities and have been reported to be an important component of the diet of many juvenile fish species in the estuarine waters. There is limited of information on the distribution of this important fauna in Sri Lankan estuarine waters and mysids are not included in biodiversity lists. Present study was conducted to record the mysid species inhabit in the estuarine systems from western and north-western region of Sri Lanka as a novel study. Surveys were undertaken from southwest to north-west coastal region of Sri Lanka starting from March 2012 to July 2013. From this study, four species of mysids were identified, i.e., Mesopodopsis zeylanica, M. orientalis, possibly new Siriella sp. and Anisomysis sp. mysids were found only in western and northwestern regions of Sri Lanka within nine major estuarine bodies. Number of species and their abundance recorded vary with different estuarine waters. It was noted that mysid habitats are very specific and they were absent from the sites where estuarine boundary without or limited riparian vegetations. Future management measures will be required to protect this important estuarine fauna in Sri Lanka. Keywords: Riparian vegetation, Mysids, Estuarine fauna

Harpacticoida (Copepoda) of the northern East Sea (the Sea of Japan) and the southern Sea of Okhotsk: diversity, taxocenes, and biogeographical aspects

Based on novel data and a literature review, an inventory of Harpacticoida from the northern part of the East Sea and the southern part of Sea of Okhotsk is compiled. A total of 151 species belonging to 70 genera and 26 families, of which 16 species are deemed to be new to science, are recognized from the region. Twelve harpacticoid species assemblages are described from marine and brackish water soft sediments and the phytal zone. Estuarine faunas were similar throughout the East Sea and Sea of Okhotsk, both in species composition and dominant-taxon structure. Conversely, the fauna of marine soft sediment and phytal zones differed greatly throughout this region. This distinction may have been caused by differences in dispersal rates or by differences in environmental conditions. The distribution of littoral and sublittoral harpacticoids was determined primarily by climatic factors and the temperature of surface waters. Three basic sub-regions were distinguished within the survey area: Korean, which includes many tropical taxa (39%) and a smaller amount (about 20%) of boreal taxa; Primorye, where boreal and subarctic-arctic species (>40%) predominate, and representatives of the tropical complex are rare (17%); and Soya, with a mix of tropical (22%) and boreal (31%) faunal elements. The faunas of the Korean and the Primorye sub-regions are distinct, whereas that of the Soya has intermediate features.

Multiproxy approach for Holocene paleoenvironmental reconstructions from microorganisms (testate amoebae and foraminifera) and sediment analyses: The infilling of the Loire Valley in Nantes (France)

Foraminifera and testate amoebae are jointly used with sediment characteristics (sediment size, calcium carbonate, C, H, N and S proportions, and clay mineralogy) to reconstruct the Holocene sediment infilling of the Loire estuary (Nantes, France). The results reveal the infilling of the Loire Valley during the Holocene. Deposited on the Hercynian substratum, the first deposits are made of gravels with rare associated fauna. This corresponds to the gravel lag usually present as basal deposits in the river course. The clay mineralogy indicates an erosion of the substratum. Then, from 8850 to 5850 cal. yr BP, estuarine fauna settled in a laminated sediment that alternates between clay and sand. The smectite associated with kaolinite and illite suggests increased input from the Sèvre Nantaise River. The fauna progressively shifts from estuarine to marine, indicating a rise in the sea level. From 5850 cal. yr BP, the pace of the sea level rise slowed and channels migrated, implying intense erosion. After 2100 cal. yr BP, the fauna was dominated by testate amoebae, indicating a continentalization of the environment. The top samples reflect recent human activity and urbanization.

Addition of passive acoustic telemetry mitigates lost data from satellite-tracked manatees

Satellite-tracked manatees routinely lose satellite tags or tag functionality, resulting in the loss of valuable data on migration and habitat use patterns. Fortunately, some movement data from these animals remain salvageable because manatees typically retain a peduncle belt containing an acoustic transmitter that can be detected with a submersible hydrophone. We deployed an array of moored datalogging hydrophones at key locations in our study area to detect manatee belt-embedded acoustic transmitters, a technique not typically used to track manatees. Our array was successful in detecting five tagged manatees, and concurrently detected compatible acoustic tags of other estuarine fauna (e.g. Bull Sharks) tagged by local researchers. Moored datalogging hydrophones, therefore, provided a method to mitigate the loss of satellite tags from estuarine megafauna, and enhanced collaborative opportunities with researchers who tagged other species using compatible equipment.

NEW DATA ABOUT MACROZOOBENTHOS OF BEYSUGSKY ESTUARY (SEA OF AZOV)

Abstract. Aim. Beysugsky Estuary is one of the biggest estuaries of the Azov-Kuban’ lowland. Like the other water bodies in the South of Russia, this one is subject to strong anthropogenic load: detachment of the freshwater part for establishing the Beysug spawning area; regulation of the flow of the rivers feeding the estuary; destruction of the Yasenskaya spit and narrowing of the Bugaz mouth; disorganized tourism. The ongoing reformation of the ecosystem makes it necessary to carry out the analyses of the modern state of the biota of this water body and uncover reasons and regularities of its change. Location. Beysug Estuary of the Sea of Azov. Methods. Quantitative zoobenthos samples were taken with the Petersen dredger (sampling area 0,034 m2) from board of the inflatable “Zodiac” boat. Qualitative samples were taken in the coastal zone by hand and with the dredge. All the samples taken were washed through the bag made of mill sieve with mesh size 0,5 mm, and then were fixed in a plastic bucket by 4 % formaldehyde (quantitative samples) or 70 % ethyl alcohol (qualitative samples). Taking and processing of samples were carried out in field and laboratory environment using common methods. 22 samples at 7 stations were taken in total. Results. Macrozoobenthos was presented by 14 invertebrate species. Estuarine fauna is the depleted version of the euryhaline one of the Sea of Azov with Holocene relic macrophyte-dwelling elements. Biodiversity and quantitative characters of the estuarine communities decrease from west to east. Pelophylic detritophages predominated in the benthic communities of the estuary. The results of this research are meant to be used for uncovering historical ways of forming of benthic fauna and clearing up the dependence of community structure on the seawater influence, freshwater flow, regulation of freshwater and seawater sources, nature of changing of faunas at salinization of estuaries connected with the sea and the river network by the system of channels. Main conclusions. Major factors effecting composition, structure and distribution of benthic communities in the Beysug Estuary are: 1) bottom sediments’ structure (mostly clayey silts of pelite and, in certain parts, alevropelite fractions; 2) bathymetry of the water body (70 % of the estuary presented by 0,6–1 m depths, southern part of the estuary up to 2 m); 3) salinity, which varies from 6 ‰ in the east up to 10 ‰ in the west; 4) presence of macrophytes, solitarily occurring in the western part of the estuary.

Quantifying Florida Bay habitat suitability for fishes and invertebrates under climate change scenarios.

The Florida Bay ecosystem supports a number of economically important ecosystem services, including several recreational fisheries, which may be affected by changing salinity and temperature due to climate change. In this paper, we use a combination of physical models and habitat suitability index models to quantify the effects of potential climate change scenarios on a variety of juvenile fish and lobster species in Florida Bay. The climate scenarios include alterations in sea level, evaporation and precipitation rates, coastal runoff, and water temperature. We find that the changes in habitat suitability vary in both magnitude and direction across the scenarios and species, but are on average small. Only one of the seven species we investigate (Lagodon rhomboides, i.e., pinfish) sees a sizable decrease in optimal habitat under any of the scenarios. This suggests that the estuarine fauna of Florida Bay may not be as vulnerable to climate change as other components of the ecosystem, such as those in the marine/terrestrial ecotone. However, these models are relatively simplistic, looking only at single species effects of physical drivers without considering the many interspecific interactions that may play a key role in the adjustment of the ecosystem as a whole. More complex models that capture the mechanistic links between physics and biology, as well as the complex dynamics of the estuarine food web, may be necessary to further understand the potential effects of climate change on the Florida Bay ecosystem.

Atlantic extreme wave events during the last four millennia in the Guadalquivir estuary, SW Spain

A multidisciplinary study from a number of drilled cores in the Guadalquivir estuary has made possible to identify as many as three extreme wave events and their facies in the 4th millennium BP (A: ~4000calyr BP, B: ~3550calyr BP, and C: ~3150calyr BP). These events, which caused strong erosion in the Guadalquivir sandy barrier and in the neighboring aeolian systems of El Abalario, brought about significant paleogeographical changes that may have affected human settlements established in the area during the Neolithic and Copper Age periods and during the Middle Bronze Age. The three events can be spatially correlated and their facies differentiated from more proximal to more distal from the coastline. The most proximal facies is characterized by a massive accumulation of shells, a sandy or sandy–muddy matrix, an erosive base, a highly diverse mixture of species (marine and estuarine), and lithoclasts. The most distal facies presents a muddy–sandy matrix, dominance of estuarine fauna, shell accumulation, presence of terrestrial species, mudpebbles, pebbles in a clayey matrix, and bioturbation. The evidence presented will further advance scientific knowledge about the impact of extreme wave events on coastal areas in SW Iberia and NW Africa.

Molluscan Community Recovery in a New England Back‐Barrier Salt Marsh Lagoon 10 Years after Partial Restoration

AbstractLike many Eastern U.S. salt marshes, East Harbor salt marsh lagoon on Cape Cod was isolated from tidal flow in the 1800s, resulting in near‐freshwater conditions and loss of native salt marsh species. After its partial restoration in 2002, a variety of marine and estuarine fauna recolonized East Harbor, and soft shell clam (Mya arenaria) recolonization was particularly prolific. The goal of our study was to evaluate molluscan community composition, density, and distribution at regular intervals for 10 years following restoration, and to relate molluscan community recovery to various physical properties at the site. In 2007, 2008, and 2011, we sampled mollusks at several points across East Harbor, and we also recorded water salinity and temperature, particle size distribution, and submerged aquatic vegetation density. In 2007 and 2008, we encountered 12 and 11 mollusk species, respectively; M. arenaria was the most abundant species in 2007 and the second most abundant species in 2008. In 2011, we encountered eight mollusk species and M. arenaria was the most abundant species. Mollusk species richness declined from 12 to 8 species between 2008 and 2011. Our results show that mollusk species richness and density have declined significantly since the first few years following restoration; related studies attribute this to high summer water temperatures in the Main Lagoon and severe macroalgal blooms during 2005–2006. This suggests that East Harbor is still equilibrating to baseline conditions and that full tidal restoration may be necessary to sustain a diverse mollusk community at East Harbor.

Variation in Estuarine Consumer Communities Along An Assembled Eutrophication Gradient: Implications for Trophic Instability

A eutrophication gradient was assembled from four spring-fed estuaries and four surface-fed estuaries to determine whether changes in zooplankton and hyperbenthos abundance along the gradient were gradual or abrupt. For 1 year in each estuary, monthly faunal surveys were conducted during nighttime flood tides using oblique plankton-net tows, producing abundance data for 316 taxa. Indicator taxa for the spring-fed and surface-fed groups were identified from a combination of abundance and encounter frequencies. Seventeen of the 20 strong indicator taxa for the spring-fed group (85 %) were benthic, whereas 10 of the 13 strong indicators for the surface-fed group (77 %) were plankton-oriented. The eight communities were ordinated by canonical analysis of principal coordinates (CAP); the estuarine faunas were found to be uniquely distributed along the principal CAP axis. Success of blind reclassification of plankton samples to their respective estuaries of origin ranged from 75 to 100 % (mean, 91 %). Given the assembled gradient was composed of distinctive communities that were distributed across a broad range of trophic states, the transition between benthic and plankton-oriented indicators was investigated and found to be abrupt, with strong shifts occurring nearer the oligotrophic end of the gradient. The CAP ordination agreed with trends in light attenuation, but not dissolved oxygen. We conclude that the abrupt faunal shifts were likely related to differences in basal resource (primary producer) availability brought about by differences in light environment. Abrupt loss of benthic basal resources will affect benthic consumers and those plankton-oriented consumers that intermittently depend on benthic biomass pathways whenever plankton-based pathways are unproductive.

Influence of habitat structure and mouth dynamics on avifauna of intermittently-open estuaries: A study of four small South African estuaries

Habitat composition was a major factor in determining waterbird species composition and abundance, particularly the area of floodplain and vegetated channel in four intermittently open estuaries (IOEs) in the warm-temperate coastal biogeographical region of South Africa. Average bird densities on the four estuaries varied from 0.5 to 4.2 birds per hectare, and community composition differed significantly between estuaries. However, the considerable variation in abundance of macrophytes did not have a detectable effect on waterbirds. Under closed mouth conditions, piscivorous birds dominated the avifauna. Each estuary's avifauna responded differently in terms of changes in feeding guild composition when the mouth opened. Bird abundance changed immediately after breaching, but not consistently. Diversity was significantly higher under open-mouth conditions for three of the four estuaries, and species composition was significantly different from that under closed-mouth conditions at all four estuaries. Changes in mouth dynamics as a result of climate change, water abstraction and artificial breaching could lead to significant changes in estuarine fauna.

조류가 강한 서해 하구에서 수동어구를 이용한 하구역 유영생물의 효율적 채집

To obtain the effective sampling estuarine fauna by a passive net in the West Sea of Korea occurring strong tide, catch were collected by bag nets with various sampling trials off Ganghwa Island in November 2009. We compared the difference of community structures (on spring tide vs. neap tide, total sample vs. subsample and 4 nets vs. 1 net) with each species composition as a sampling unit by the Pearson chi-square test. Number of individual at the spring tide was more abundant than that at the neap tide (p<0.0001) although number of species at the spring tide was not significantly different with that at the neap tide (p=0.174). Both number of species (p=0.138) and number of individual (p=0.096) were not significantly different between total sample and random subsample. Number of species was not significantly different between the subsample by 1 net and the subsample by 4 nets (p=0.515), but number of individual was a little different on both samples (p=0.024). In conclusion, we suggest the subsample by 1 net at spring tide as the effective sampling estuarine fauna by a passive net in the West Sea occurring strong tide.

Estuarine biodiversity as an indicator of groundwater discharge

Communities located in the interface between marine/brackish and freshwater habitats are likely to be early responders to climatic changes as they are exposed to both saline and freshwater conditions, and thus are expected to be sensitive to any change in their environmental conditions. Climatic effects are predicted to reduce the availability of groundwater, altering the hydrological balance on estuarine-aquifer interfaces. Here, we aimed to characterise the estuarine faunal community along a gradient dependent on groundwater input, under a predicted climatic scenario of reduction in groundwater discharge into the estuary. Sediment macrofauna was sampled along a salinity gradient following both the wet and dry seasons in 2009. Results indicated that species abundance varied significantly with the salinity gradient created by the groundwater discharge into the estuarine habitat and with sampling time. The isopode Cyathura carinata (Krøyer, 1847) and the polychaetes Heteromastus filiformis (Claparède, 1864) and Hediste diversicolor O.F. Muller, 1776 were associated with the more saline locations, while oligochaeta and Spionidae were more abundant in areas of lower salinity. The polychaete Alkmaria romijni Horst, 1919 was the dominant species and ubiquitous throughout sampling stations. This study provides evidence for estuarine fauna to be considered as a potentially valuable indicator of variation in the input of groundwater into marine-freshwater interface habitats, expected from climatic pressures on aquifer levels, condition and recharge rates. For instance, a reduction in the abundance of some polychaete species, found here to be more abundant in freshwater conditions, and increasing Oligochaeta found here on higher salinities, can potentially be early warnings of a reduction in the input of groundwater into estuaries. Estuarine benthic species are often the main prey for commercially important fish predators such as in our case study, making it important to monitor the aquatic habitat interfaces taking into consideration the estuarine macrobenthos and groundwater availability in the system.

The role of vicariance and dispersal on New Zealand's estuarine biodiversity: the case of Paracorophium (Crustacea: Amphipoda)

To investigate the role of vicariance and dispersal on New Zealand’s estuarine biodiversity, we examined variability in mitochondrial cytochrome c oxidase subunit I (COI) gene sequences for the amphipod genus Paracorophium. Individuals from the two nominate endemic species (Paracorophium excavatum and Paracorophium lucasi) were collected from sites throughout the North and South Islands. Sequence divergences of 12.8% were detected among the species. However, divergences of up to 11.7% were also observed between well supported clades, suggesting the possibility of cryptic species. Nested clade analyses identified four distinct lineages from within both P. excavatum and P. lucasi, with boundaries between clades corresponding to topographical features (e.g. Cook Straight, North and East Cape). Sequence divergences of 3.7–4.9% were also observed within geographic regions (e.g. east and west coasts of the upper North Island). Genetic structure in Paracorophium appears to represent prolonged isolation and allopatric evolutionary processes dating back to the Upper Miocene and continuing through the Pliocene and early Pleistocene. On the basis of molecular clock estimates from sequence divergences and reconstructions of New Zealand’s geological past, we suggest that sea level and landmass changes during the early Pleistocene (2 Mya) resulted in the isolation of previously contiguous populations leading to the present-day patterns. COI genetic structure was largely congruent with previously observed allozyme patterns and highlights the utility of COI as an appropriate marker for phylogeographic studies of the New Zealand estuarine fauna. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 103, 863–874.

Plastic debris ingestion by marine catfish: An unexpected fisheries impact

Plastic marine debris is a pervasive type of pollution. River basins and estuaries are a source of plastics pollution for coastal waters and oceans. Estuarine fauna is therefore exposed to chronic plastic pollution. Three important catfish species [Cathorops spixii (N=60), Cathorops agassizii (N=60) and Sciades herzbergii (N=62)] from South Western Atlantic estuaries were investigated in a tropical estuary of the Brazilian Northeast in relation to their accidental ingestion of plastic marine debris. Individuals from all three species had ingested plastics. In C. spixii and C. agassizii, 18% and 33% of individuals had plastic debris in their stomachs, respectively. S. herzbergii showed 18% of individuals were contaminated. All ontogenetic phases (juveniles, sub-adults and adults) were contaminated. Nylon fragments from cables used in fishery activities (subsistence, artisanal and commercial) played a major role in this contamination. These catfish spend their entire life cycles within the estuary and are an important feeding resource for larger, economically important, species. It is not yet possible to quantify the scale and depth of the consequences of this type of pollution. However, plastics are well known threat to living resources in this and other estuaries. Conservation actions will need to from now onto take plastics pollution into consideration.

Population density, survival and movement of blue crabs in estuarine salt marsh nurseries

The importance of a broad suite of complex structured habitats as nurseries for estuarine fauna is well recognized. In contrast, recent evidence indicates the nursery value of salt marshes and contiguous unvegetated mud flats for blue crabs are underestimated. To assess the nursery value of salt marsh tidal creeks for the blue crab Callinectes sapidus in coastal North Carolina, USA, we quantified population density, survival and movement patterns of juvenile blue crabs in 2 tidal salt marsh creeks during summer and fall. Survival rates of blue crab juveniles were high (0.98 d–1) and similar in both creek systems. Juvenile crabs exhibited a high degree of site fidelity to a given marsh creek during summer–fall, suggesting that losses were predominantly due to mortality, not emigration. Our study provides critical information on the demographic processes underlying the importance of salt marshes as nurseries for estuarine-dependent species, and was novel in that it: (1) measured density, survival and emigration concurrently; and (2) enabled the identification of individuals, which allowed for the assessment of the relationship between blue crab size, survival and capture probability. We conclude that the observed patterns of abundance, survival and habitat utilization of blue crabs within tidal salt marsh creeks in North Carolina are consistent with the hypothesis that salt marsh creeks are important nurseries for blue crabs. Further, the relatively high use of the marsh surface by juvenile blue crabs, combined with a general lack of directed sampling within these complex habitats, suggests that crab densities may be even higher in salt marshes than previously thought.

A quantitative assessment of the response of mobile estuarine fauna to crab-tiles during tidal immersion using remote underwater video cameras

Laying artificial materials on the shore to create refugia that attract crustaceans is a ‘fishing’ technique known mainly from South America and the UK. In the UK, this method of fishing is known as ‘crab-tiling’, which involves laying of roof tiles, pieces of guttering or car tyres (‘crab-tiles’) intertidally in estuaries to provide habitat for Carcinus maenas. Crabs are then harvested for use as angling bait. C. maenas are known to reside under crab-tiles during low tide, however the extent to which crab-tiles influence the distribution and behaviour of crabs and other estuarine fauna during high tide is not clear. To investigate this, fixed underwater video cameras were deployed on a mudflat over two separate occasions in control (non-tiled) and tiled sites. Crabs were significantly more abundant in crab-tiled sites than control sites, and they remained relatively stationary, travelling less in tiled sites than those in control sites. The abundance of mobile fauna (e.g. benthic gobies, mysids, crabs and pelagic fishes) was greater in control sites than in tiled sites during July. The same trend was observed in March but was not significant. Diversity (number of taxa) tended to be greater in control sites than tiled sites on both occasions, but the trend was not significant. The faunal assemblage was not different between control and tiled treatments in either March or July. Crabs occupied crab-tiles throughout high tide immersion, and qualitative observations indicated a tendency to aggressively defend particular tiles. It also seems likely that the tiles provided some protection for the crabs from fish and diving birds.

A survey of the estuarine benthic fauna of Homebush Bay, Parramatta River, N.S.W.

It has been suggested that the area surrounding Homebush Bay, which contains extensive mangrove and saltmarsh habitat, be converted into a Bicentennial Park for Sydney. In 1978 the Municipal Council of Strathfield, Auburn and Concord commissioned a report dealing with this proposal from Macquarie University (Anon., 1978). Although the report covered certain physical and ecological data as well as management proposals, no survey of the estuarine invertebrate fauna was carried out. This study remedies that situation by reporting on a survey conducted in Homebush Bay by the Coast and Wetlands Society on the 14 November 1982.