Fish Nursery Research Articles

Functional reorganization of marine fish nurseries under climate warming.

While climate change is rapidly impacting marine species and ecosystems worldwide, the effects of climate warming on coastal fish nurseries have received little attention despite nurseries' fundamental roles in recruitment and population replenishment. Here, we used a 26-year time series (1987-2012) of fish monitoring in the Bay of Somme, a nursery in the Eastern English Channel (EEC), to examine the impacts of environmental and human drivers on the spatial and temporal dynamics of fish functional structure during a warming phase of the Atlantic Multidecadal Oscillation (AMO). We found that the nursery was initially dominated by fishes with r-selected life-history traits such as low trophic level, low age and size at maturity, and small offspring, which are highly sensitive to warming. The AMO, likely superimposed on climate change, induced rapid warming in the late 1990s (over 1°C from 1998 to 2003), leading to functional reorganization of fish communities, with a roughly 80% decline in overall fish abundance and increased dominance by K-selected fishes. Additionally, historical overfishing likely rendered the bay more vulnerable to climatic changes due to increased dominance by fishing-tolerant, yet climatically sensitive species. The drop in fish abundance not only altered fish functional structure within the Bay of Somme, but the EEC was likely impacted, as the EEC has been unable to recover from a regime shift in the late 1990s potentially, in part, due to failed replenishment from the bay. Given the collapse of r-selected fishes, we discuss how the combination of climate cycles and global warming could threaten marine fish nurseries worldwide, as nurseries are often dominated by r-selected species.

Communities of Phytoplankton Viruses across the Transition Zone of the St. Lawrence Estuary.

The St. Lawrence hydrographic system includes freshwater, brackish, and marine habitats, and is the largest waterway in North America by volume. The food-webs in these habitats are ultimately dependent on phytoplankton. Viral lysis is believed to be responsible for a major part of phytoplankton mortality. To better understand their role, we characterized the diversity and distribution of two viral taxa infecting phytoplankton: the picornaviruses and phycodnaviruses. Our study focused on the estuary transition zone, which is an important nursery for invertebrates and fishes. Both viral taxa were investigated by PCR amplification of conserved molecular markers and next-generation sequencing at six sites, ranging from freshwater to marine. Our results revealed few shared viral phylotypes between saltwater and freshwater sites. Salinity appeared to be the primary determinant of viral community composition. Moreover, our analysis indicated that the viruses identified in this region of the St. Lawrence diverge from classified viruses and homologous published environmental virotypes. These results suggest that DNA and RNA viruses infecting phytoplankton are likely active in the estuary transition zone, and that this region harbors its own unique viral assemblages.

Using otolith microchemistry to assess nursery habitat contribution and function at a fine spatial scale

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 606:151-173 (2018) - DOI: https://doi.org/10.3354/meps12765 Using otolith microchemistry to assess nursery habitat contribution and function at a fine spatial scale Janet A. Ley*, Holly J. Rolls Fish and Wildlife Research Institute, Florida Fish and Wildlife Conservation Commission, 100 Eighth Avenue Southeast, St. Petersburg, Florida 33701, USA *Corresponding author: danceswithfish.jal@gmail.com ABSTRACT: Estuarine tributaries are vital links in connectivity for transient coastal fish undergoing ontogenetic habitat shifts, yet these resources are on the frontlines of anthropogenic change. Prioritizing actions to protect valuable fisheries may require fine-scale analyses of the relative value and function of tributaries as nurseries for regional populations. For sectioned otoliths from young-of-the-year (YOY) common snook Centropomus undecimalis; snook), we used laser ablation-inductively coupled plasma-mass spectrometry and stable isotope analysis to obtain microchemical signatures distinguishing 9 tributaries (each <1.0 km2, <5 km apart) along a mangrove-to-saltmarsh gradient in the Little Manatee River (LMR), Florida, USA. Using canonical analysis of principal coordinates and jackknifed leave-one-out classification for 123 fish, 70 (56.9%) were classified correctly based on microchemical signatures, compared with 11.1% that would have been correctly classified by chance alone (χ2, p < 0.0001). Months later, 39 of 40 (98%) yr-1 snook collected from throughout the LMR were assigned to a YOY nursery tributary based on otolith core signatures. The 3 tributaries making the greatest contribution of YOY snook to the yr-1 population were in pristine, low salinity (0.5-1.5 psu) saltmarshes farthest from the estuary mouth. Since other studies have identified completely different spatial patterns in fish nursery use from year to year, this study should be replicated to assess temporal variation in snook contribution from these nurseries. Nevertheless, this fine-scale application of otolith microchemistry is encouraging for future efforts seeking to protect locations having the greatest likelihood of contributing to survival of fishes that make ontogenetic habitat shifts within coastal ecosystems. KEY WORDS: Otolith microchemistry · Mangrove · Salt marsh · Ecology · Estuary · Centropomus undecimalis · Nursery · Tampa Bay · Connectivity · Contribution analysis Full text in pdf format Supplementary material PreviousNextCite this article as: Ley JA, Rolls HJ (2018) Using otolith microchemistry to assess nursery habitat contribution and function at a fine spatial scale. Mar Ecol Prog Ser 606:151-173. https://doi.org/10.3354/meps12765 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 606. Online publication date: November 15, 2018 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2018 Inter-Research.

Juvenile fish caging as a tool for assessing microplastics contamination in estuarine fish nursery grounds.

Estuaries serve as nursery grounds for many marine fish species. However, increasing human activities within estuaries and surrounding areas lead to significant habitat quality degradation for the juveniles. In recent years, plastic pollution has become a global environmental issue as plastic debris are found in all aquatic environments with potential adverse impacts on marine biota. Given the important ecological role of estuaries and implications of microplastics (MP) in ecosystems, here we assess the occurrence, number, size, and polymer types of MP ingested by wild and caged juvenile European flounder (Platichthys flesus). We deployed caged fish for 1month at five sites in three estuaries in the eastern English Channel. The Seine estuary, heavily impacted by manmade modifications and one of the most contaminated estuaries in Europe, was compared to two smaller estuaries (Canche and Liane) less impacted by industrial activities. We found that juvenile flounders (7-9cm) were vulnerable to plastic ingestion. Seventy-five percent of caged fish and 58% of wild caught fish had the presence of MP items in their digestive tract. Fibers (69%) dominated in the fish's digestive tract at all sites. An average of 2.04 ± 1.93 MP items were ingested by feral juvenile flounder and 1.67 ± 1.43 by caged juvenile flounder. For the caged fish, the three sites impacted by wastewater treatment plant (Liane, Le Havre harbor, and Rouen) were those with the highest percentage of individuals that has ingested MP items. Most of the isolated items were fibers and blue in color. Polymers identified by micro Raman spectroscopy were polycaprolactam, polyethylene terephthalate, and polyurethane. Although other environmental factors may have affected caged fish condition and mortality, we found no significant correlation with the number of ingested MP. However, the high occurrence of MP ingested by juvenile fish on nursery grounds raises concerns on their potential negative effects for fish recruitment success and population renewal. Finally, this study describes, for the first time, the feasibility of using caged juvenile fish as an assessing tool of MP contamination in estuarine nursery grounds.

Exploring the demarcation requirements of fish breeding and nursery sites to balance the exploitation, management and conservation needs of Lake Victoria ecosystem

AbstractFisheries resources in vital freshwater ecosystems have been reported to be under immense threat, resulting in conflicts between conservation, management and exploitation. This study established requirements for identifying and mapping fish breeding and nursery grounds in such ecosystems in the Kenyan part of Lake Victoria. The criteria were characterised by the use of indigenous knowledge, field data, literature on breeding sites, macroinvertebrates distribution, larval and relative fish abundances, digitisation, participatory mapping, and periodic sampling. Data were collected from trawl and seine net surveys. Digitisation and mapping of the proposed conservation sites were carried out using Quantum GIS software. Participatory physical demarcation of sites was done using buoys and markers. Larval and juvenile fishes were diverse and abundant in all seven river mouths and six bays surveyed with little variance; an important aspect of breeding areas. Additionally, a preponderance of macroinvertebrates and high fish diversity compared with offshore sites in the lake strengthened the hypothesis that these are critical habitats for spawning and preferred habitats for nurseries for fish. The approach can be adopted globally to guarantee the long‐term integrity of critical fish habitats for sustainable fisheries management and blue growth.

Mapping and Classification of Ecologically Sensitive Marine Habitats Using Unmanned Aerial Vehicle (UAV) Imagery and Object-Based Image Analysis (OBIA)

Nowadays, emerging technologies, such as long-range transmitters, increasingly miniaturized components for positioning, and enhanced imaging sensors, have led to an upsurge in the availability of new ecological applications for remote sensing based on unmanned aerial vehicles (UAVs), sometimes referred to as “drones”. In fact, structure-from-motion (SfM) photogrammetry coupled with imagery acquired by UAVs offers a rapid and inexpensive tool to produce high-resolution orthomosaics, giving ecologists a new way for responsive, timely, and cost-effective monitoring of ecological processes. Here, we adopted a lightweight quadcopter as an aerial survey tool and object-based image analysis (OBIA) workflow to demonstrate the strength of such methods in producing very high spatial resolution maps of sensitive marine habitats. Therefore, three different coastal environments were mapped using the autonomous flight capability of a lightweight UAV equipped with a fully stabilized consumer-grade RGB digital camera. In particular we investigated a Posidonia oceanica seagrass meadow, a rocky coast with nurseries for juvenile fish, and two sandy areas showing biogenic reefs of Sabelleria alveolata. We adopted, for the first time, UAV-based raster thematic maps of these key coastal habitats, produced after OBIA classification, as a new method for fine-scale, low-cost, and time saving characterization of sensitive marine environments which may lead to a more effective and efficient monitoring and management of natural resources.

Fully Dynamic Input-Output/System Dynamics Modeling for Ecological-Economic System Analysis

The complexity of ecological-economic systems significantly reduces our ability to investigate their behavior and propose policies aimed at various environmental and/or economic objectives. Following recent suggestions for integrating nonlinear dynamic modeling with input-output (IO) modeling, we develop a fully dynamic ecological-economic model by integrating IO with system dynamics (SD) for better capturing critical attributes of ecological-economic systems. We also develop and evaluate various scenarios using policy impact and policy sensitivity analyses. The model and analysis are applied to the degradation of fish nursery habitats by industrial harbors in the Seine estuary (Haute-Normandie region, France). The modeling technique, dynamization, and scenarios allow us to show trade-offs between economic and ecological outcomes and evaluate the impacts of restoration scenarios and water quality improvement on the fish population.

Habitat partitioning in juvenile fishes associated with three vegetation types in selected warm temperate estuaries, South Africa

Three common vegetation types were studied to assess habitat partitioning in juvenile fishes in select warm temperate estuaries of South Africa. Vegetated habitat types are known as productive and important areas for predator avoidance and feeding and are often preferred by juvenile fishes. Habitat partitioning is not well understood, with previous studies mostly focusing on seagrass (Zostera capensis). This study aimed to assess three common vegetated fish nursery areas in estuaries to aid conservation planning. Fishes were collected by means of double-winged, six-hooped fyke nets, 1 mm mesh size secured in placed on the nocturnal flood tide at each inundated vegetation type (Phragmites australis, Zostera capensis, Spartina maritima) and at an adjacent unvegetated site for three consecutive months in 2014 and 2015 during the summer recruitment period for juvenile fishes. Higher catches were frequently recorded in vegetated areas for solely estuarine and marine estuarine dependent species. In general, the previously unstudied reed, P. australis showed the highest species richness and abundance of juvenile fishes overall, followed by, Z. capensis and the intertidal salt marsh species, S. maritima. Results from this study supports international trends on the value of vegetated areas as refugia for young fishes in estuaries.

Trophic structure and microbial activity in a spawning area of Engraulis encrasicolus

The abundance, biomass and size-structure of planktonic populations, and the microbial metabolic processes were studied in the Sicily Channel, one of the most important spawning areas in the Mediterranean for anchovy (Engraulis encrasicolus), a pelagic species of commercial interest. Results showed that prokaryotes contribute for the 83% of total carbon biomass. Microphytoplankton abundances and biomasses were dominated by autotrophic nanoflagellates and dinoflagellates (36 identified species) and contribute 11% of total biomass. The microzooplanktonic biomass showed its maximum at the surface or subsurface and its contribution was low (4%). In agreement with the general oligotrophy of the investigated area, the study highlights the prevalence of pico-sized fractions within the whole phytoplankton biomass expressed as chlorophyll content, suggesting the importance of picophytoplankton in sustaining the microbial food web. At the same time, the levels of microbial hydrolytic activities are related to productive processes recycling the organic matter and releasing nutrients (P and N), indicating also an active functioning of ecosystem at low trophic levels. Autotrophic production exceeded oxidation by respiration; at the same time, the co-variation of prokaryotic activities and eggs distribution with temperature in summer was observed. The results obtained confirmed that the area acted as a nursery for small fish and both autotrophic and heterotrophic processes supported by microorganisms were in synergy.

Seascape connectivity and the influence of predation risk on the movement of fishes inhabiting a back‐reef ecosystem

AbstractThe mangrove–seagrass–patch reef (MSP) ecosystem serves as the principal back‐reef nursery for many reef fishes in the Caribbean, but the functional roles of habitats that form this seascape remain unclear. We assessed ecosystem and trophic connectivity of two common reef fishes (schoolmaster, Lutjanus apodus; white grunt, Haemulon plumierii) and one predator (great barracuda, Sphyraena barracuda) in a Caribbean MSP ecosystem using acoustic telemetry and natural dietary tracers. Triangulated positions from an acoustic positioning system indicated that L. apodus and H. plumierii relied on multiple habitats within this MSP ecosystem, occupying areas with more cover (lower risk) during the day and areas with less cover (higher risk) at night. During the day, both species exhibited limited movement away from structured habitats (e.g., mangroves, patch reef) and avoided the primary activity space of S. barracuda in the central channel over sand bottom or seagrass. At night, L. apodus moved into the channel and adjacent seagrass beds on the margin of this high‐risk area when S. barracuda occurrence was reduced, suggesting that this species adjusts its foraging activities to minimize encounter rates with predators. Haemulon plumierii also displayed distinct day–night shifts with directed movements at twilight across higher risk habitat to nighttime locations in seagrass. Conspicuous changes in the rate of movement were also detected at different times of the day, and observed mismatches between movement rates of S. barracuda and our two potential prey species appeared to be a behavioral response to reduce their vulnerability. Dietary tracer analysis supported the premise that observed shifts to nocturnal habitats were associated with foraging, with significant contributions of organic matter derived from nighttime locations. Findings from this study clearly demonstrate that the configuration of habitats and spatiotemporal variability in predation risk are key determinants of movement and foraging activities for these species, indicating that an improved understanding of seascape connectivity is critical to the management of reef‐dependent species.

Effect of The Phytase Enzyme Addition in The Artificial Feed on Digestibility of Feed, Feed Conversion Ratio and Growth of Gift Tilapia Saline Fish (Oreochromis niloticus) Nursery Stadia I

The purpose of this study was to determine the effect of adding the phytase enzyme in the artificial feed on digestibility of feed, feed conversion ratio and growth of gift tilapia saline fish (Oreochromis niloticus) nursery stadia I. The fish samples in this study used gift tilapia saline fish (O. niloticus) with an average weight of 0,62 ± 0,008 g/fish and the stocking density of 1 fish1 L. Experimental method used in this study was completely randomized design with 4 treatments and 3 repetitions. The treatments were by adding phytase enzyme in artificial feed with the different level of doses those were A (0 FTU kg1 feed), B (500 FTU kg1 feed), C (1000 FTU kg1 feed) and D (1500 FTU kg1 feed). The results show that the addition of phytase enzyme was significantly (P<0.01) affected on apparent digestibility coefficient of protein (ADCP), apparent digestibility coefficient of Phospor (ADCF), feed conversion ratio (FCR), protein efficiency ratio (PER), and relative growth rate (RGR), on the other hand it insignificantly (P>0.05) affected on Survival Rate (SR) of gift tilapia saline fish. The optimum doses of phytase enzyme on RGR, FCR, PER, ADCP and ADCF of gift tilapia saline fish ranged from 1060 to 1100 FTU kg-1 feed.

Do nursery habitats provide shelter from flow for juvenile fish?

Juvenile fish nurseries are an essential life stage requirement for the maintenance of many fish populations. With many inshore habitats globally in decline, optimising habitat management by increasing our understanding of the relationship between juvenile fish and nursery habitats may be a prudent approach. Previous research on post–settlement snapper (Chrysophrys auratus) has suggested that structure may provide a water flow refuge, allowing snapper to access high water flow sites that will also have a high flux of their pelagic prey. We investigated this hypothesis by describing how Artificial Seagrass Units (ASUs) modified water flow while also using a multi–camera set up to quantify snapper position in relation to this water flow environment. Horizontal water flow was reduced on the down–current side of ASUs, but only at the height of the seagrass canopy. While the highest abundance of snapper did occur down–current of the ASUs, many snapper also occupied other locations or were too high in the water column to receive any refuge from water flow. The proportion of snapper within the water column was potentially driven by strategy to access zooplankton prey, being higher on the up–current side of ASUs and on flood tides. It is possible that post–settlement snapper alternate position to provide opportunities for both feeding and flow refuging. An alternative explanation relates to an observed interaction between post–settlement snapper and a predator, which demonstrated that snapper can utilise habitat structure when threatened. The nature of this relationship, and its overall importance in determining the value of nursery habitats to post–settlement snapper remains an elusive next step.

Cuban land use and conservation, from rainforests to coral reefs

Cuba is an ecological rarity in Latin America and the Caribbean region. Its complex political and economic history shows limited disturbances, extinctions, pollution, and resource depletion by legal or de facto measures. Vast mangroves, wetlands, and forests play key roles in protecting biodiversity and reducing risks of hazards caused or aggravated by climate change. Cuba boasts coral reefs with some of the region's greatest fish biomass and coral cover. Although it has set aside major protected areas that safeguard a host of endemic species, Cuba's environment is by no means pristine. Through much of its early history, deforestation and intensive agricultural production under colonial then neocolonial powers was the norm. Using remote sensing, we find Cuba's land today is 45% devoted to agricultural, pasturage, and crop production. Roughly 77% of Cuba's potential mangrove zone is presently in mangrove cover, much of it outside legal protection; this is likely the most intact Caribbean mangrove ecosystem and an important resource for coastal protection, fish nurseries, and wildlife habitat. Even the largest watersheds with the most agricultural land uses have a strong presence of forests, mangroves, and wetlands to buffer and filter runoff. This landscape could change with Cuba's gradual reopening to foreign investment and growing popularity among tourists-trends that have devastated natural ecosystems throughout the Caribbean. Cuba is uniquely positioned to avoid and reverse ecosystem collapse if discontinuities between geopolitical and ecosystem functional units are addressed, if protection and conservation of endemic species and ecosystems services accompany new development, and if a sound ecological-restoration plan is enacted.

A Simple Method to Show the Economic and Educational Value of Wildlife and Wildlands

A Simple Method to Show the Economic and Educational Value of Wildlife and Wildlands

Influencia humana en las fluctuaciones poblacionales de erizos de mar

Echinoids play an important role in marine ecosystems structuring. Often, their population density experience markedly fluctuations that promote a state shift in the ecosystems they inhabit. Population increments of some sea urchins may cause catastrophic changes in temperate areas of the planet by decimating the erect macroalgae cover. These population increments results in unproductive and very stable assemblages, known as “blanquizales” (ericeras/moradales), or sea urchin barren ground. Macroalgae are the main ecosystem engineers in temperate areas and generate a suitable nursery and feeding habitat for fishes. These algae stands are also important zones for biofiltration of coastal waters and CO2 uptake. The main consequence of vegetated biomass lost is a trophic disequilibrium that generates important economic losses for artisanal fisheries and tourism. In tropical areas, sea urchin’s outbreaks can cause bioerosion in coral reefs. However, the most important event to highlight was the mass mortality occurred in the Caribbean during the 80’s. This event favored the development of algae communities that suffocated the coral reef ecosystem. Therefore, both in temperate and tropical areas of the planet, these boom-bust echinoids generate undesired ecosystems states. Very recently, various global scale collaborative papers have highlighted a clear anthropogenic cue. Human activity though overfishing or favoring global warming, weakens marine ecosystem resilience and promote these catastrophic ecosystem shifts. To mitigate the effects of these population changes different management strategies have been used. For instance, in temperate areas, sea urchin reduction actions (manually or by using quick lime), sea urchin harvesting or the implementation of marine reserves have been used, with contrasting results. In Caribbean coral reefs affected by urchin mass mortality, some sea urchin juvenile’s reintroduction plans have been used but with very low effectiveness. The more feasible ecosystem scale strategy due to its preventive nature, seems to be the implementation of protected areas. However, the impact of global warming will exceed our capacity to manage marine ecosystems locally and will required more efficient global actions to prevent undesired sea urchin fluctuations. Rev. Biol. Trop. 65(Suppl. 1): S23-S34. Epub 2017 November 01.

Changes in zooplankton community, and seston and zooplankton fatty acid profiles at the freshwater/saltwater interface of the Chowan River, North Carolina.

The variability in zooplankton fatty acid composition may be an indicator of larval fish habitat quality as fatty acids are linked to fish larval growth and survival. We sampled an anadromous fish nursery, the Chowan River, during spring of 2013 in order to determine how the seston fatty acid composition varied in comparison with the zooplankton community composition and fatty acid composition during the period of anadromous larval fish residency. The seston fatty acid profiles showed no distinct pattern in relation to sampling time or location. The mesozooplankton community composition varied spatially and the fatty acid profiles were typical of freshwater species in April. The Chowan River experienced a saltwater intrusion event during May, which resulted in brackish water species dominating the zooplankton community and the fatty acid profile showed an increase in polyunsaturated fatty acids (PUFA), in particular eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The saltwater intrusion event was followed by an influx of freshwater due to high precipitation levels in June. The zooplankton community composition once again became dominated by freshwater species and the fatty acid profiles shifted to reflect this change; however, EPA levels remained high, particularly in the lower river. We found correlations between the seston, microzooplankton and mesozooplankton fatty acid compositions. Salinity was the main factor correlated to the observed pattern in species composition, and fatty acid changes in the mesozooplankton. These data suggest that anadromous fish nursery habitat likely experiences considerable spatial variability in fatty acid profiles of zooplankton prey and that are correlated to seston community composition and hydrodynamic changes. Our results also suggest that sufficient prey density as well as a diverse fatty acid composition is present in the Chowan River to support larval fish production.

Increase in predation risk and trophic level induced by nocturnal visits of piscivorous fishes in a temperate seagrass bed

The majority of surveys on food webs of aquatic ecosystems have been conducted during the day owning to difficulties in sampling animals at night. In this study, to examine diurnal changes in predator-prey interactions in a temperate seagrass Zostera marina bed, a quantitative day/night survey of fish, the dominant animal community, coupled with acoustic telemetry of their predators, was conducted. The number of species, abundance, and biomass of piscivorous predators and mean trophic level during the night were significantly higher than those in the day in all seasons. Analysis of the stomach contents of 182 piscivorous predators showed that no fish predation occurred during the day whereas predation occurred during the night in winter, spring, and summer. Acoustic telemetry demonstrated nocturnal visits by dominant piscivorous fish species (rockfishes and conger eel) to the seagrass bed. We conclude that the nocturnal visits by piscivorous fishes increased the predation risk and trophic level in the fish nursery. The ecological functions of seagrass beds should be reevaluated accounting for day/night changes in food webs; these areas serve as nurseries for juvenile and small-sized fishes during the day and as foraging grounds for predators during the night.

Distribution, Spread, and Habitat Predictability of a Small, Invasive, Piscivorous Fish in an Important Estuarine Fish Nursery

Invasive species often cause negative ecological and economic effects. Florida has &gt;20 established invasive fish species but only seven exist in saltwater. The present study examined Belonesox belizanus (Pike Killifish), a Central American euryhaline fish introduced to Tampa Bay (west-central Florida) in the early 1990s, which has quantifiably reduced populations of small-bodied native fishes and may compete with prized sportfish juveniles in estuarine nursery habitat. Long-term monitoring revealed that B. belizanus occurs in estuarine waterbodies along a 31-km stretch of the bay’s eastern fringe, with a second, smaller population in two western tributaries. Spread rate was estimated to be 5.5–13 km year−1, intermediate among invasive poeciliids. A novel implementation of boosted regression tree modeling to assess B. belizanus habitat predictability found greater probability of presence with decreasing water depth and pH, whereas presence tended to be greatest at polyhaline salinity. It is hypothesized that B. belizanus distribution in Tampa Bay is constrained by deep, seawall habitats acting as ecological barriers. Further B. belizanus spread therefore may be most likely to occur by human release (from aquaria or bait buckets) or bird carry-off. Newly restored tidal habitat within the current range probably will be invaded quite quickly by B. belizanus.

Diversity and community structure of fish, plankton and benthos in Karangsong Mangrove Conservation Areas, Indramayu, West Java, Indonesia

Sihombing VS, Gunawan H, Sawitri R.2017. Diversity and community structure of fish, plankton and benthos in Karangsong Mangrove Conservation Areas, Indramayu, West Java, Indonesia. Biodiversitas 18: 601-608. The Karangsong Mangrove Conservation Area in Indramayu District, West Java, Indonesia, extending across 20 hectares of coastal land, has undergone eight years of managed revegetation. It has a variety of productive habitats that support the availability of fish resources. The research described in this paper was conducted in July 2016 with the purpose of assessing the diversity, evenness, and structure of fish, plankton and benthos communities as an indicator of the effectiveness of the rehabilitation of the mangrove ecosystem. The fish, benthos, and plankton were collected and analyzed in the Biotrop Laboratories. Fish sampling was carried out using a gill net with mesh size of 25 mm, and with traps. Juvenile fish were collected using a fish net with mesh size of 15 mm, by combing the water column horizontally for 10-15 minutes in the morning and afternoon. For plankton sampling a net No. 25 was used, while samples of benthos were collected using an Ekman Grab sampler. To calculate the community structure and diversity of fish, the study used ecological indices (abundance, dominance, constancy and ecological significance) and diversity indices (Shannon and Simpson diversity). A total of 413 individuals were obtained from 18 fish species, representing 16 families. Family Lutjanidae and Acanthuridae had the highest representative number of species and Pomacentridae showed the highest relative abundance of individuals. The value for the fish diversity index was 2.44 and for the species evenness index was 0.84. The fish population consisted of 44.44% omnivores, 38.89% carnivores and 16.67% herbivores/ detritivores. The highest density of plankton was accounted for by Bacillariophyceae (78.57%), followed by Chlorophyceae (14.29%) and Zooplankton (7.14%). The diversity index for the plankton (H) ranged between 1.040 and 1.462 across habitats, while the evenness index (E) ranged between 0.144 and 1.22. The benthos consisted of Gastropods (83.58%), Crustacea (3.28%), Palaemonidae (1.64%) and Oligochaeta (11.48%). The diversity index for the benthos ranged from 0. 939 to 1. 199 and the evenness index from 0.158 to 0.207. Hence, it may infer from the domination of the environment by Bacillariophyceae and Gastropods, and the low values for diversity index and evenness index, that the area is not particularly good as a fish nursery and breeding habitat. Nevertheless, there are two species of fish that exhibit potential productivity in every habitat; they are Chanos chanos and Scatophagus argus.

Evidence for Habitat Residency and Isotopic Niche Partitioning in a Marine-Estuarine-Dependent Species Associated with Mangrove Habitats from the East Coast of South Africa

Estuaries are valuable fish nurseries due, primarily, to an abundance of food and the provision of shelter in a spatially heterogeneous area. Habitats within estuaries, however, vary in their specific supply of these two factors with more structurally complex habitats tending to offer more of both food and refuge. In this study, we investigated the site residency of an abundant estuarine-dependent sparid, Rhabdosargus holubi, from two nearby but dissimilar mangrove habitats using two approaches: mark-recapture and stable isotope analysis. Results showed that rates of residency for both short- (in the order of days) and long-term (weeks) were high. Stable isotope ratios (carbon and nitrogen) were also used to compare the isotopic niche of two size groups between the two mangrove habitats. Both small and larger juveniles from a more complex creek associated with red mangroves and seagrass had a significantly broader isotopic niche width when compared with the groups from the more homogenous white mangrove habitat. R. holubi appear to establish strong residency at sites soon after recruitment which may persist until their departure from the estuary despite apparent differences in habitat quality.