Local ecological knowledge of shellfish collectors in an extractivist reserve,Northeast Brazil: implications for co-management

The Local Ecological Knowledge of shellfish harvesters in a Northern Brazil estuary was recorded to provide socio-ecological information for the development of a co-management system. The research was carried out in the community of Acaú, Paraiba state, from January to October 2015, and involved 120 shellfish harvesters (average age 44 years). Participant observations, interviews, questionnaires, free lists, and participatory mapping were used. Shellfishes were mostly collected by women as their main source of income. Most shellfish extraction sites were closest to the community and provided easy access to the resource. Twelve species of mollusks are collected, with Anomalocardia flexuosa being the most targeted species, with the highest Cognitive Salience Index—it stood out due to its relevance in terms of economic and cultural importance. The fishers stated that their main difficulties were transporting shellfish, health problems, low price and lack of buyers during winter. They would like to see the implementation of a fishery closure subsidized by unemployment insurance. We suggest that implementing management measures in conjunction with fishers’ input would be more effective than decisions based on scientific evidence alone.

     

Impact of a flood event on the zooplankton of an estuarine lake

Shallow coastal lakes are prone to large fluctuations in physico-chemical variables such as salinity and turbidity. This is now escalating in response to global change. A flood event in March 2014 resulted in a silt plume spreading through part of Lake St Lucia (South Africa). To determine the impact of this event on zooplankton, the Narrows region of St Lucia was sampled on a monthly basis from March to September 2014. For comparative purposes, data from samples collected prior to the flood event were included in the analyses. Analysis of similarity (ANOSIM) revealed dissimilarities in zooplankton community structure among the sampling occasions. The March 2014–May 2014 period was characterized by the highest abundance of freshwater species. Conversely, the abundance of the resident St Lucia copepods Acartiella natalensis and Oithona brevicornis was lowest during this time, and highest in September 2014. The other dominant copepod Pseudodiaptomus stuhlmanni prevailed in March 2014, but declined markedly in April. As of September 2014, P. stuhlmanni had yet to regain its pre-flood densities. The BIOENV procedure, which relates biological and environmental data, revealed that turbidity, salinity and dissolved oxygen were responsible for the observed changes in zooplankton community structure during the study period. Careful management of turbidity and salinity is stressed, as both factors are major drivers of the biota of St Lucia and similar systems worldwide.     

The influence of zooplankton food resources on the morphology of the estuarine clupeid Gilchristella aestuarius (Gilchrist, 1914)

Synopsis The body shape of the estuarine clupeidGilchristella aestuarius from the St. Lucia system is different from that of the same species in other estuaries. The morphology ofG. aestuarius is discussed in relation to long term food availability in the St. Lucia system.     

THE PROBLEM OF NOMENCLATURE

Whitfield, A. K. &; Blaber, S. J. M. 1978. Feeding ecology of piscivorous birds at Lake St Lucia, Part 3: Swimming birds. Ostrich 50:10-20. The diets, foraging periodicities and feeding behaviour of the Reed Cormorant Phalacrocorax africanus, Whitebreasted Cormorant Phalacrocorax carbo and White Pelican Pelecanus onocrotalus were studied at Lake St Lucia, Natal, South Africa, during 1975 and 1976. The Reed Cormorant fishes in shallow water within 100 m of the shore and mainly caught Sarotherodon mossambicus and Solea bleekeri, while the Whitebreasted Cormorant caught Mugilidae, Rhabdosargus sarba and Thryssa vitrirostris in deeper water. The diet of the White Pelican followed three distinct phases: a pre-incubation phase when the birds followed and preyed heavily on migrating Mugil cephalus shoals; an incubation and post-incubation phase when the adults flew a round trip of 200 km to the north to obtain freshwater fish, mainly cichlids, from the Pongolo pans where fishes were concentrated and densities high; and a post-fledgling phase when both adults and juveniles fed on a variety of marine species of fish in Lake St Lucia for about a month before dispersing to other areas. The feeding and breeding of Reed Cormorants and White-breasted Cormorants is discussed in relation to wind speeds, water turbidity and flooding of backwaters. The diet and long-range foraging behaviour of White Pelicans at St Lucia are compared with data from other African lakes. The breeding season of White Pelicans at St Lucia is related to availability of fish and inaccessibility of the breeding site to predators. The latter is determined by lake levels.     

St Lucia Whiptail Lizard Cnemidophorus vanzoi (Sauria: Teiidae) microsatellite primers

Eight polymorphic microsatellite loci have been characterized for the endangered St Lucia Whiptail Lizard Cnemidophorus vanzoi. Endemic to two small islets, Maria Major and Maria Minor, off the coast of St Lucia, Lesser Antilles, the world population is estimated at < 1000 individuals. However, representatives of the systematically complex genus Cnemidophorus, containing sexual species and parthenogenetic allopolyploids, are distributed widely in North, Central and South America, and on several islands in the Caribbean Sea. These microsatellite markers are being used to monitor the genetic structure of a population of St Lucia Whiptails, recently founded through translocation, on the nearby Praslin Island.     

The impact of scallop drags on sea urchin populations and benthos in the Bay of Fundy,Canada

The fishery for the green sea urchin (Strongylocentrotus droebachiensis) began in New Brunswick in the late 1980s in response to increasing demand from Asian markets, primarily Japan. Fishing was initiated by members of the scallop industry and the harvesting practices were based on familiar fishing gear (scallop drags or dredges) and similar operations occurring simultaneously in Maine. Because of the potential impact of scallop gear on the shallow water populations in areas not traditionally fished, a study was initiated in 1993 to document (1) the proportion of sea urchins damaged during the harvesting operation, (2) the impact on and subsequent recovery time of the associated benthic flora and epifauna, and (3) the impacts on the bottom substrate. Two sites were chosen for the study based on a split-plot design with a control and experimental plot at each site. In each experimental plot, a towing lane was created parallel to shore. Divers used a fixed line transect method to survey the control and treatment plots prior to and after the harvesting operation done with commercial scallop Digby drags. Further diver-based surveys were done 3 and 6 months later. Results showed a significant decrease in sea urchin densities and an increase in the number of broken sea urchin tests after the harvesting operation at the Passamaquoddy Bay and Grand Manan sites (3–15%). On both sites, there were significant changes in the density of mobile predators such as lobsters, crabs, whelks and sculpins. Lobster density declined to zero after dragging, but the lack of body parts suggested they moved out of the area. Whelks were observed to move into each of the experimental areas, likely in response to probable increase in available food. The dragging operation increased the breakage rate of the kelp, Laminaria longicruris. From the study we concluded that there were short-term impacts from dragging, but the observable effects on the bottom from the single dragging event were gone in less than 3 months. The longer-term effects of dragging were unknown.     

Genetics and shell morphometrics of assimineids (Mollusca,Caenogastropoda, Truncatelloidea) in the St Lucia Estuary,South Africa

The Assimineidae are a family of amphibious microgastropods that can be mostly found in estuaries and mangroves in South Africa. These snails often occur in great numbers and are ecologically important to the St Lucia Estuary, which forms a crucial part of the iSimangaliso Wetland Park, a UNESCO World Heritage Site. Genetic and shell morphometric analyses were conducted on individuals collected from nine localities distributed from the northern lake regions to the southern lake and the mouth of the St Lucia estuarine lake. Mitochondrial (COI) and nuclear (28S) DNA was used to construct Bayesian Inference, Neighbour-joining, Maximum Parsimony and Maximum Likelihood trees. Principal Component Analysis and Cluster Analysis were performed on standard shell parameter data. Results indicate that two different taxa are present in St Lucia. The taxon comprising individuals from the South Lake and St Lucia Estuary Mouth is identified as Assiminea cf. capensis Bartsch, in accordance with the latest taxonomic consensus. The taxon comprising assimineid individuals from False Bay, North Lake and South Lake, is here tentatively named “Assiminea” aff. capensis (Sowerby). These two taxa exhibit patterns of spatial overlap that appear to vary depending on environmental parameters, particularly salinity. The need to resolve the complex taxonomy of assimineids is highlighted.     

Sea urchin vault structure,composition, and differential localization during development

Background  

Vaults are intriguing ribonucleoprotein assemblies with an unknown function that are conserved among higher eukaryotes. The Pacific coast sea urchin, Strongylocentrotus purpuratus, is an invertebrate model organism that is evolutionarily closer to humans than Drosophila and C. elegans, neither of which possesses vaults. Here we compare the structures of sea urchin and mammalian vaults and analyze the subcellular distribution of vaults during sea urchin embryogenesis.     

Fibronectin from the ovary of the sea urchin,Pseudocentrotus depressus

Summary Fibronectin, with a subunit molecular weight of 220,000 daltons, was isolated from the ovary of the sea urchin,Pseudocentrotus depressus, using affinity chromatography on heat-denatured mammalian collagen coupled to Sepharose 4B. The distribution of fibronectin in the sea urchin ovary was examined by indirect immunofluorescence using antifibronectin serum. The basement membrane and the connective tissues exhibited strong fluorescence. The fibronectin was localized closely together with collagen bundles in the sea urchin ovary. Biochemical and immunological examinations indicate that sea urchin fibronectin has similar properties as those of mammalian fibronectin.     

Testing the generality of the trophic cascade paradigm for sea otters: a case study with kelp forests in northern Washington,USA

Trophic cascade hypotheses for biological communities, linking predation by upper trophic levels to major features of ecological structure and dynamics at lower trophic levels, are widely subscribed and may influence conservation policy. Few such hypotheses have been evaluated for temporal or spatial generality. Previous studies of sea otter (Enhydra lutris) predation along the outer coast of North America suggest a pattern, often elevated to the status of paradigm, in which sea otter presence leads to reduced sea urchin (Strongylocentrotus spp.) biomass and rapid increases in abundance and diversity of annual algal species, followed by a decline in diversity as one or a few perennial algal species become dominant. Both sea otter predation and commercial sea urchin harvest are ecologically and economically important sources of urchin mortality in nearshore benthic systems in northern Washington marine waters. We recorded changes in density of macroalgae in San Juan Channel, a marine reserve in the physically protected inland waters of northern Washington, resulting from three levels of experimental urchin harvest: (1) simulated sea otter predation (monthly complete harvest of sea urchins), (2) simulated commercial urchin harvest (annual size-selective harvest of sea urchins), and (3) no harvest (control). The two experimental urchin removal treatments did not significantly increase the density of perennial (Agarum and Laminaria) or annual (Desmarestia, Costaria, Alaria and Nereocystis) species of macroalgae after 2 years, despite significant and persistent decreases in urchin densities. Our results suggest that other factors such as grazing by other invertebrates, the presence of dense Agarum stands, and recruitment frequency of macroalgae and macroinvertebrates may play a large role in influencing community structure in San Juan Channel and other physically protected marine waters within the range of sea otters. Handling editor: J. Trexler     

MANAGING THE ST. LUCIA ESTUARY—MESSAGES FROM THE MUD

Summary

The infaunal macrobenthic community of the St Lucia estuary has been exposed to natural disturbance in the form of salinity fluctuations arising from floods and hypersaline conditions, and human-induced interference arising from dredging and beam trawling. The responses of the benthos to these disturbances have been recorded between 1983 and 1994 and are discussed in the light of management options for the estuary. A simple benthic sampling strategy is suggested to monitor the important benthic species.     

Identification and characterization of PlAlix,the Alix homologue from the Mediterranean sea urchin Paracentrotus lividus

The sea urchin provides a relatively simple and tractable system for analyzing the early stages of embryo development. Here, we use the sea urchin species, Paracentrotus lividus, to investigate the role of Alix in key stages of embryogenesis, namely the egg fertilization and the first cleavage division. Alix is a multifunctional protein involved in different cellular processes including endocytic membrane trafficking, filamentous (F)‐actin remodeling, and cytokinesis. Alix homologues have been identified in different metazoans; in these organisms, Alix is involved in oogenesis and in determination/differentiation events during embryo development. Herein, we describe the identification of the sea urchin homologue of Alix, PlAlix. The deduced amino acid sequence shows that Alix is highly conserved in sea urchins. Accordingly, we detect the PlAlix protein cross‐reacting with monoclonal Alix antibodies in extracts from P. lividus, at different developmental stages. Focusing on the role of PlAlix during early embryogenesis we found that PlAlix is a maternal protein that is expressed at increasingly higher levels from fertilization to the 2‐cell stage embryo. In sea urchin eggs, PlAlix localizes throughout the cytoplasm with a punctuated pattern and, soon after fertilization, accumulates in larger puncta in the cytosol, and in microvilli‐like protrusions. Together our data show that PlAlix is structurally conserved from sea urchin to mammals and may open new lines of inquiry into the role of Alix during the early stages of embryo development.     

Distribution anomalies in avian haemosporidian parasites in the southern Lesser Antilles

We compared the haemosporidian parasite faunas (Plasmodium and Haemoproteus) of small land birds on the islands of St Lucia, St Vincent and Grenada in the southern Lesser Antilles. The islands differ in distance from the South American source of colonists, proximity to each other, and similarity of their avifaunas. On each island, we obtained 419–572 blood samples from 22–25 of the 34–41 resident species. We detected parasite infection by PCR and identified parasite lineages by sequencing a portion of the mitochondrial cytochrome b gene. Parasite prevalence varied from 31% on St Lucia to 22% on St Vincent and 18% on Grenada. Abundant parasite lineages differed between the three islands in spite of the similarity in host species. As in other studies, the geographic distributions of the individual parasite lineages varied widely between local endemism and broad distribution within the West Indies, including cases of long‐distance disjunction. St Vincent was unusual in the near absence of Plasmodium parasites, which accorded with low numbers of suitable mosquito vectors reported from the island. Parasites on St Vincent also tended to be host specialists compared to those on St Lucia and Grenada. Similarity in parasite assemblages among the three islands varied in parallel with host assemblage similarity (but not similarity of infected hosts) and with geographic proximity. Parasite prevalence increased with host abundance on both St Lucia and St Vincent, but not on Grenada; prevalence did not vary between endemic and more widespread host species. In addition, the endemic host species harbored parasites that were recovered from a variety of non‐endemic species as well. These results support the individualistic nature of haemosporidian parasite assemblages in evolutionarily independent host populations.     

Experimental evidence that herbivory increases shoot density and productivity in a subtropical turtlegrass (Thalassia testudinum ) meadow

The sea urchin, Lytechinus variegatus, has been estimated to consume between 50 and 90% of annual net aboveground production in selected turtlegrass (Thalassia testudinum) meadows in the eastern Gulf of Mexico. Nevertheless, turtlegrass persists where sea urchin grazing is intense. We hypothesized that turtlegrass productivity is stimulated by grazing, as has been reported from terrestrial grassland systems, and that this best explains the persistence of heavily grazed turtlegrass in St. Joseph Bay, Fla. This hypothesis was tested by manipulating sea urchin densities (0, 10, and 20 individuals/m²) in 1-m² enclosures. These densities encompass the range of average densities at the study site and those reported in the literature. Changes in turtlegrass abundance (e.g., short shoot density and biomass), production by short shoots, and leaf width were monitored in these enclosures during the summer. Repeated-measures ANOVA showed that production by short shoots, leaf density/shoot, and leaf width decreased over time in all treatments. Leaf density/shoot and leaf width were not significantly impacted by grazing, nor did grazing significantly reduce seagrass biomass, but it did lead to significantly higher densities of short shoots than found in control cages. Our results indicate that turtlegrass compensates for the effects of sea urchin herbivory by increasing the recruitment of short shoots during the growing season. We estimate that this increased shoot density led to a 40% increase in net aboveground primary production (g dry weight/m²) in grazing treatments, which helps to explain the lack of significant reductions of sea grass biomass during the growing season. Received: 26 April 1995 / Accepted: 29 May 1997     

Effects of removing sea urchins (Strongylocentrotus droebachiensis): Stability of the barren state and succession of kelp forest recovery in the east Atlantic

Stability properties of the barren state of a kelp forest-sea urchin system were studied in northern Norway. The ability of the sea urchin Strongylocentrotus droebachiensis to maintain high population densities and recover from perturbations, and the succession of kelp forest revegetation, were studied experimentally by reducing the sea urchin density on a barren skerry. Additional information was obtained from community changes following a natural, but patchy, sea urchin mortality that varied between sites. On the barren grounds, high sea urchin densities (30 50 per m²) is maintained by annual recruitment. Severe reductions of sea urchin densities initiated luxuriant kelp growth, while more moderate reductions allowed establishment of opportunistic algae (during spring and early summer), but no kelps. Succession of algal growth, after the severe decline in sea urchin densities, followed a predictable pattern. At first the substrate was colonized by filamentous algae, but within few weeks they were outcompeted by the fast growing kelp Laminaria saccharina. After 3–4 years of the removal experiment, the slower-growing, long-lived kelp L. hyperborea became increasingly dominant. Increased food availability after reduction in sea urchin density led to increased individual growth of the remaining sea urchins. However, the population density did not increase, neither from recruitment nor immigration from adjacent areas with high sea urchin densities. Possibly, early establishment of a dense kelp stand, may represent a breakpoint in the ability of sea urchins to reestablish a barren state. The ability of L. saccharina quickly to invade and monopolize an area may have both positive and negative effects on the succession towards the climax L. hyperborea kelp forest. Competitive interactions may slow the process, but development of a dense stand of L. saccharina will also reduce grazing risk on scattered recruits of the more slowly growing L. hyperborea.     

Impact of Aquaculture on Commercial Fisheries: Fishermen’s Local Ecological Knowledge

The Bay of Fundy along the southwest coast of New Brunswick, Canada is one of the most densely stocked finfish aquaculture areas in the world. An inshore multi-species fishery that dates back to the earliest European settlement shares these waters, and has been the economic mainstay of coastal communities. These inshore fishermen are increasingly displaced by the expanding aquaculture industry. A recent study conducted among fishermen in Southwest New Brunswick recorded their observations about the environmental impact of finfish aquaculture and the consequences for their commercial fishery. Fishermen all reported significant environmental degradation around aquaculture sites. Within 2 years of an operation being established, fishermen reported that gravid female lobsters as well as herring avoid the area, scallop and sea urchin shells become brittle, scallop meat and sea urchin roe becomes discolored. The use of chemicals to control sea lice on farmed salmon has also caused lobster, crab and shrimp kills. These and other concerns suggest that more comprehensive and detailed studies are required to establish the environmental and economic interactions of aquaculture and the inshore fishery, as well as on the stocks on which that fishery rely. The study also points to the need for more effective use of fishermen’s knowledge in designing such studies.     

Demographic implications of predatory wrasses on low-density Diadema antillarum populations

This study evaluates and projects the effect of experimental removal of two species of wrasses, Thalassoma bifasciatum and Halichoeres bivittatus, on the demographic structure of the Caribbean sea urchin Diadema antillarum. For census periods ‘before’ and ‘after’ fish removal at treatment and un-manipulated control sites, size-based matrix population projections revealed the most important change in the sea urchin demography was increased survival of the medium size-class following removal of wrasses. The asymptotic growth rate (λ) exhibited no differences between periods for the control; however, the treatment displayed a significant increase in λ from 0.94 to 1.0. During the before period, the treatment population displayed lower λ than the control population, indicating site differences in urchin recruitment from the outset of the experiment, however after one year of maintenance of the predator removal treatment, the treatment population exhibited and increased growth rate to become similar to the control population; indicating predatory-release for the treatment population. Physiological status of sea urchins, as determined by righting times, exhibited no difference between treatment and control populations, or through time. Nil correlation was evident between righting activity and urchin size, indicating that urchin physiological status was not influenced by predation. Long-term demographic simulation indicated that the sea urchin population growth at the treatment site was negative and thus unviable predatory wrasse. However, only one year after fish removal, sea urchin population growth rate became positive. Therefore local population recovery for D. antillarum appears enhanced when abundance of wrasses is kept low.     

SOME NOTES ON THE BIRDS OF THE KAOKOVELD

Whitfield, A. K. &; Blaber, S. J. M. 1978. Feeding ecology of piscivorous birds at Lake St Lucia, Part 1: Diving birds. Ostrich 49:185-198.

The diets of three species of diving piscivorous birds at Lake St Lucia, Natal, South Africa during 1975 and 1976 are described and related to availability and abundance of different prey species. Mugilidae and Clarias gariepinus were the chief prey of the Fish Eagle Haliaeetus vocifer, while Johnius belengcrii and Sarotherodon mossambicus were, respectively, the main food items of Caspian Terns Hydroprogne tschegruva, and Pied Kingfishers Ceryle rudis. The methods of prey capture used by the three species of birds are described.

Predation on particular species of fish was related primarily to their swimming depth, abundance, size and distribution in littoral areas. Fishing habits, densities and foraging periodicity of the birds are discussed with regard to physical parameters such as thermals, wind speeds and water turbidity. The timing of breeding seasons at Lake St Lucia is related to fish densities, lake levels, turbidity of the water and air temperatures.     

Predation and the Control of the Sea Urchin Echinometra viridisand Fleshy Algae in the Patch Reefs of Glovers Reef, Belize

The massive reduction in sea urchin Diadema antillarum populations since the mid-1980s has been associated with large increases in the abundance of fleshy algae on many Caribbean reefs despite the availability of other sea urchin and finfish grazers. This study examined the ecology of a grazer living sympatrically with D. antillarum, the common and abundant sea urchin Echinometra viridis. I examined the role that finfish and invertebrate predators play in controlling the distribution of E. viridis as well as the ability of this sea urchin to control exposed fleshy algae on the patch reefs of the Glovers Reef Atoll lagoon. I found that the major predators of this sea urchin were Calamus bajonado (jolthead porgy), Balistes vetula and Canthidermis sufflamen (queen and ocean triggerfish), Lachnolaimus maximus (hogfish), and a gastropod, probably Cassis madagascariensis. The abundance of E. viridis is constrained by predation, which restricts E. viridis to cryptic locations, such as crevices. Sea urchins bit a smaller percentage of experimental algal assays than finfish. Finfish herbivory was associated positively with patch reef topographic complexity. Unexpectedly, E. viridis abundance was positively correlated with fleshy algal abundance, but negatively correlated with the frequency of finfish bites. Predators restrict E. viridis to crevices and therefore reduce their influence on exposed fleshy algae, even at moderately high population densities (up to 10 per square meter). Since net benthic primary production of coral reefs is most strongly associated with herbivory on exposed surfaces, it would appear that E. viridis is unable to maintain the same production as reefs dominated by D. antillarum. Received 5 November 1998; accepted 2 June 1999.