Sexual Reproduction and Early Development in the Estuarine Sea Anemone, Nematostella vectensis Stephenson, 1935

This dissertation: 1) determines the factor(s) responsible for spawning induction in NematosteJla vectensis; 2) isolates, describes, and documents the source of jelly from egg masses of N. vectensis; and 3) describes N. vectensis' early development. Namatostella vectensis were maintained on a 7-day mussel feeding/water change regime over 159 days. Within 36 hours of mussel feeding/water change. 69.1% of females and 78.5% of males spawned reliably. Through manipulation of feeding, water change, oxygen and nitrogenous waste concentrations, spawning induction was found to be triggered by the oxygen concentration associated with water change, and not by feeding. Ammonia, anemones' major waste product, inhibited this induction in a concentration-dependent manner. Female N. vectensis release eggs in a persistent jellied egg mass which is unique among the Actiniaria. The major component of this egg mass jelly was a positive periodic acid-Schiffs staining, 39.5-40.5 kD glycoprotein. Antibodies developed in rabbits against this glycoprotein bound to jelly of intact egg masses and to granules (~ 2.8 IJm in diameter) present in female anemone mesenteries and their associated filaments. Antibodies did not label male tissues. Nematostella vecfensis embryos underwent first karyokinesis -60 minutes following the addition of sperm to eggs. Second nuclear division took place, followed by first cleavage, 90-120 minutes later. Each of the 4 blastomeres that resulted from first cleavage contained a single nucleus. Arrangement of these blastomeres ranged from radial to pseudospiral. Embryonic development was both asynchronous and holoblastic. Following formation of the 4-cell stage, 71% of embryos proceeded to cleave again to form an 8-cell stage. In each of the remaining 29% of embryos, a fusion of from 2-4 blastomeres resulted in 4 possible patterns which had no affect on either cleavage interval timing or subsequent development. The fusion event was not due to ooplasmic segregation. Blastomeres isolated from 4-celled embryos were regulative and developed into normal planula larvae and juvenile anemones that were 1/4 the size of those that developed from intact 4-celled embryos. Embryos exhibiting the fusion phenomenon were examined at the fine structural level. The fusion phenomenon resulted in formation of a secondary syncytium and was not a mere compaction of blastomeres.

Ichthyoplankton survey of the estuarine and inshore waters of the Florida Everglades, May 1971 to February 1972

Quarterly ichthyoplankton sampling was conducted at 16 estuarine and 24 inshore stations along the Florida Everglades from May 1971 to February 1972. The area is one of the most pristine along lhe Florida coast. The survey provided the first comprehensive information on seasonal occurrence, abundance (under 10 m' of surface area), and distribution of fish eggs and larvae in this area. A total of 209,462 fish eggs and 78,865 larvae was collected. Eggs were identified only as fish eggs, but among the larvae, 37 families, 47 genera, and 37 species were identified. Abundance of eggs and larvae, and diversity of larvae, were greatest in the inshore zone. The 10 most abundant fish families which together made up 90.7% of all larvae from the study area were, in descending order of abundance: Clupeidae, Engraulidae, Gobiidae, Sciaenidae, Carangidae, Pomadasyidae, Cynoglossidae, Gerreidae, Triglidae, and Soleidae. Clupeidae, Engraulidae, and Gobiidae made up 59.9% of all larvae. The inshore zone (to a depth of about 10 m) was a spawning ground and nursery for many fishes important to fisheries. The catch of small larvae (<>3.5 mm SL) indicated that most fishes identified from the 10 most abundant families spawned throughout the inshore zone at depths of <> 10 m, but Orthopristis chrysoptera, Gerreidae, and Prionotus spp. spawned at depths > 10 m, with offshore to inshore (eastward) larval transport. Salinity was one of several environmental factors that probably limited the numbers of eggs and larvae in the estuarine zone. Abundance of eggs and larvae at inshore stations was usually as great as, and sometimes greater than, the abundance of eggs and larvae at offshore stations (due west of the Everglades). (PDF file contains 81 pages.)

Identification of West African estuarine shrimp and crab larvae

The paper deals with the decapod crustacean larvae likely to be found in fresh and brackish waters in tropical west Africa. It summarizes results from an ongoing program of describing larvae hatched directly from adults of known species, to provide the identification keys necessary for applied research on nursery grounds, plankton ecology and pollution effects. A preliminary key to stage - 1 larvae is given for approximately 40 species. In includes all the genera, and nearly all the species, known to produce larvae in fresh and low-salinity waters. The common species of higher salinity waters are also included

Ecology and fishery in the Cross River Estuary - a research project

A literature review of 50 titles including nearly all relevant publications ensures adequate basis on the present level of knowledge. The proposal includes (a) the determination of the biozoenosis and selected environmental factors, and (b) of fishery and stock data of the main fish and shellfish species. The ecological research studies physical and chemical variables of the estuarine waters (flow velocity and direction, water temperature, conductivity, pH, dissolved oxygen, salinity, nutrients such as ammonium, nitrite, phosphate, silicate, pollutants such as hybrocarbons, pesticides and heavy metals, biochemical oxygen demand, chemical oxygen demand), plankton (bacterio-phyto-and zooplankton), benthos, sediment. The fishery biological and fishery investigations include: number of villages and fishermen, number of boats and gears by type, length and weight data of the main fishery objects with concentration on the shrimps, species and numbers of fish parasites. The ecological variables were monitored at fixed stations on sections in the Cross-River Estuary, Calabar and Great Kwara Rivers two times per month during spring and neap tides. The fishery biological and fishery variables were obtained during spring and neap tide too. For the determination of the detailed methodology the ecological and fishery part of the progeamme should be started with frame surveys based on a larger number of stations. These frame surveys should be repeated from time to time. Both parts of the programme are based on three years duration. It seems already appropriate to continue the work with selected representative stations, villages and variables in form of a long-term data chain

Decision support systems optimising effluent release in sub tropical estuarine environment - An Australian case study

Gold Coast Water is responsible for the management of the water and wastewater assets of the City of the Gold Coast on Australia’s east coast. Treated wastewater is released at the Gold Coast Seaway on an outgoing tide in order for the plume to be dispersed before the tide changes and renters the Broadwater estuary. Rapid population growth over the past decade has placed increasing demands on the receiving waters for the release of the City’s effluent. The Seaway SmartRelease Project is designed to optimise the release of the effluent from the City’s main wastewater treatment plant in order to minimise the impact of the estuarine water quality and maximise the cost efficiency of pumping. In order to do this an optimisation study that involves water quality monitoring, numerical modelling and a web based decision support system was conducted. An intensive monitoring campaign provided information on water levels, currents, winds, waves, nutrients and bacterial levels within the Broadwater. These data were then used to calibrate and verify numerical models using the MIKE by DHI suite of software. The decision support system then collects continually measured data such as water levels, interacts with the WWTP SCADA system, runs the models in forecast mode and provides the optimal time window to release the required amount of effluent from the WWTP. The City’s increasing population means that the length of time available for releasing the water with minimal impact may be exceeded within 5 years. Optimising the release of the treated water through monitoring, modelling and a decision support system has been an effective way of demonstrating the limited environmental impact of the expected short term increase in effluent disposal procedures. (PDF contains 5 pages)

A survey of estuarine oxygen concentrations in relation to the passage of migratory salmonids

This report presents the first attempt at a national assessment of an Environmental Quality Standard (EQS) for dissolved oxygen (DO) in estuaries with the objective of allowing the passage of migratory salmonids. Under the Control of Pollution Act, Water Authorities and River Purification Boards have powers to control discharges to estuaries and need to define an EQS for the calculation of consent conditions. The object of any such standards is to permit the existence of good quality salmonid fisheries with only very occasional restrictions to the passage of fish. The report gives brief summaries of the DO regime in estuaries, the oxygen requirements of salmonids, and of tentative standards proposed by various authorities. These standards are then compared with DO and fishery data from UK estuaries, provided by the appropriate regulatory authorities. It concludes that a minimum annual lower 95-percentile of 5.0 mg/1 will meet the objective in most estuaries, and that a lower value of 3.0 mg/1 will permit the establishment of a more restricted fishery. However, more stringent standards may be needed in estuaries containing high concentrations of toxic pollutants. containing high concentrations of toxic pollutants.

Changes in catch rates and length and age at maturity, but not growth, of an estuarine plotosid (Cnidoglanis macrocephalus) after heavy fishing

The hypothesis that heavy fishing pressure has led to changes in the biological characteristics of the estuary cobbler (Cnidoglanis macrocephalus) was tested in a large seasonally open estuary in southwestern Australia, where this species completes its life cycle and is the most valuable commercial fish species. Comparisons were made between seasonal data collected for this plotosid (eeltail catfish) in Wilson Inlet during 2005–08 and those recorded with the same fishery-independent sampling regime during 1987–89. These comparisons show that the proportions of larger and older individuals and the catch rates in the more recent period were far lower, i.e., they constituted reductions of 40% for fish ≥430 mm total length, 62% for fish ≥4 years of age, and 80% for catch rate. In addition, total mortality and fishing-induced mortality estimates increased by factors of ~2 and 2.5, respectively. The indications that the abundance and proportion of older C. macrocephalus declined between the two periods are consistent with the perception of long-term commercial fishermen and their shift toward using a smaller maximum gill net mesh to target this species. The sustained heavy fishing pressure on C. macrocephalus between 1987–89 and 2005–08 was accompanied by a marked reduction in length and age at maturity of this species. The shift in probabilistic maturation reaction norms toward smaller fish in 2005–08 and the lack of a conspicuous change in growth between the two periods indicate that the maturity changes were related to fishery-induced evolution rather than to compensatory responses to reduced fish densities.

Ichthyoplankton community structure and comparative trophodynamics in an estuarine transition zone

Surveys were conducted to evaluate and compare assemblage structure and trophodynamics of ichthyoplankton, and their variability, in an estuarine transition zone. Environmental gradients in the saltfront region of the Patuxent River subestuary, Chesapeake Bay, were hypothesized to define spatiotemporal distributions and assemblages of ichthyoplankton. Larval fishes, zooplankton, and hydrographic data were collected during spring through early summer 2000 and 2001. Larvae of 28 fish species were collected and species richness was similar each year. Total larval abundance was highest in the oligohaline region down-estuary of the salt front in 2000, but highest at the salt front in 2001. Larvae of anadromous fishes were most abundant at or up-estuary of the salt front in both years. Two ichthyoplankton assemblages were distinguished: 1) riverine—characterized predominantly by anadromous species (Moronidae and Alosinae); and 2) estuarine—characterized predominantly by naked goby (Gobiosoma bosc) (Gobiidae). Temperature, dissolved oxygen, salinity-associated variables (e.g., salt-front location), and concentrations of larval prey, specifically the calanoid copepod Eurytemora affinis and the cladoceran Bosmina longirostris, were important indicators of larval fish abundance. In the tidal freshwater region up-estuary of the salt front, there was substantial diet overlap between congeneric striped bass (Morone saxatilis) and white perch (M. americana) larvae, and also larvae of alewife (Alosa pseudoharengus) (overlap= 0.71–0.93). Larval abundance, taxonomic diversity, and dietary overlap were highest within and up-estuary of the salt front, which serves to both structure the ichthyoplankton community and control trophic relationships in the estuarine transition zone.

Spatial and temporal distribution and the potential for estuarine interactions between wild and hatchery chum salmon (Oncorhynchus keta) in Taku Inlet, Alaska

We investigated estuarine spatial and temporal overlap of wild and marked hatchery chum salmon (Oncorhynchus keta) fry; the latter included two distinct size groups released near the Taku River estuary (Taku Inlet) in Southeast Alaska (early May releases of ~ 1.9 g and late May releases of ~ 3.9 g wet weight). Our objectives were to compare abundance, body size, and condition of wild chum salmon fry and hatchery chum salmon fry raised under early and late rearing strategies in different habitats of Taku Inlet and to document environmental factors that could potentially explain the distribution, size, and abundance of these chum salmon fr y. We used a sampling design stratified into inner and outer inlet and neritic and littoral habitats. Hatchery fry were rare in the inner estuary in both years but outnumbered wild fry 20:1 in the outer estuary. Hatchery fry were significantly larger than wild fry in both littoral and neritic samples. Abundances of wild and hatchery fry were positively correlated in the outer inlet, indicating the formation of mixed schools of hatchery and wild fry. Spatial and temporal overlap was greatest between wild and early hatchery fry in the outer inlet in both habitats. The early hatchery release coincided with peak abundances of wild fry in the outer inlet, and the distribution of wild and early hatchery fry overlapped for about three weeks. Our results demonstrate that the timing of release of hatchery fry may affect interactions with wild fry.

Use of pop-up satellite archival tag technology to study postrelease survival of and habitat use by estuarine and coastal fishes: an application to striped bass (Morone saxatilis)

Pop-up satellite archival tags (PSATs) have been used to study movements, habitat use, and postrelease survival of large pelagic vertebrates, but the size of these tags has historically precluded their use on smaller coastal species. To evaluate a new generation of smaller PSATs for the study of postrelease survival and habitat use of coastal species, we attached Microwave Telemetry, Inc., X-tags to ten striped bass (Morone saxatilis) 94–112 cm total length (TL) caught on J hooks and circle hooks during the winter recreational fishery in Virginia. Tags collected temperature and depth information every five minutes and detached from the fish after 30 days. Nine of the ten tags released on schedule and eight transmitted 30% to 96% (mean 78.6%) of the archived data. Three tags were physically recovered during or after the transmission period, allowing retrieval of all archived data. All eight striped bass whose tags transmitted data survived for 30 days after release, including two fish that were hooked deeply with J hooks. The eight fish spent more than 90% of their time at depths less than 10 m and in temperatures of 6–9°C, demonstrated no significant diel differences in depth or temperature utilization (P>0.05), and exhibited weak periodicities in vertical movements consistent with daily and tidal cycles.

Diversity of estuarine movements of striped bass (Morone saxatilis): a synoptic examination of an estuarine system in southern New Jersey

We determined the dis-tribution of multiple (n=68; 508−978 mm total length [TL]) striped bass (Morone saxatilis) along the estua-rine salinity gradient in the Mullica River−Great Bay in southern New Jersey over two years to determine the diversity of habitat use and the movements of striped bass. Ultrasoni-cally tagged fish were detected in this estuarine area by means of wireless hydrophones deployed at four gates inside the entrance of the study area and farther up to tidal freshwater (38 km). Numerous individuals frequently departed and returned to the estuary, primarily in the spring and late fall over periods of 15−731 days at liberty. The period of residency and degree of movement of individuals to and from the estuary varied extensively among seasons and years. The diversity of movements in and out of, as well as within, the estuary differed from the less-complex patterns reported in earlier studies, perhaps because of the comprehensive and synoptic nature of this study.

Experiments in gear configuration to reduce bycatch in an estuarine squid-trawl fishery

Three experiments were performed in an estuarine squid-trawl fishery in New South Wales, Australia, to test modifications to trawl nets. Lateral mesh openings were experimentally increased and physical bycatch reduction devices (BRDs) were placed in codends. These modifications aimed to reduce nontargeted catches of fish, while maintaining catches of the targeted broad squid (Photololigo etheridgei) and bottle squid (Loliolus noctiluca). Compared to conventional codends made with 41-mm diamond mesh, codends made with different posterior circumferences and larger 45-mm mesh had no significant effect on the catches of any species. The best performing configurations involved the installation of BRDs designed to separate organisms according to differences in behavior. In particular, versions of a composite square-mesh panel reduced the total weight of bycatch by up to 71% and there was no significant effect on the catches of squid. The results are discussed in terms of the probable differences in behavior between fish and squid in codends. After this study, a square-mesh panel BRD was voluntarily adopted throughout the fishery.

Shifts in the estuarine demersal fish community after a fishery closure in Puget Sound, Washington

Puget Sound is one of the largest and most ecologically significant estuaries in the United States, but the status and trends of many of its biological components are not well known. We analyzed a 21-year time series of data from standardized bottom trawl sampling at a single study area to provide the first assessment of population trends of Puget Sound groundfishes after the closure of bottom trawl fisheries. The expected increase in abundance was observed for only 3 of 14 species after this closure, and catch rates of most (10) of the abundant species declined through time. Many of these changes were stepwise (abrupt) rather than gradual, and many stocks exhibited changes in catch rate during the 3-year period from 1997 through 2000. No detectable change was recorded for either temperature or surface salinity over the entire sampling period. The abrupt density reductions that were observed likely do not reflect changes in demographic rates but may instead represent distributional shifts within Puget Sound.

Marine and estuarine ecosystem and habitat classification

The Ecological Society of America and NOAA's Offices of Habitat Conservation and Protected Resources sponsored a workshop to develop a national marine and estuarine ecosystem classification system. Among the 22 people involved were scientists who had developed various regional classification systems and managers from NOAA and other federal agencies who might ultimately use this system for conservation and management. The objectives were to: (1) review existing global and regional classification systems; (2) develop the framework of a national classification system; and (3) propose a plan to expand the framework into a comprehensive classification system. Although there has been progress in the development of marine classifications in recent years, these have been either regionally focused (e.g., Pacific islands) or restricted to specific habitats (e.g., wetlands; deep seafloor). Participants in the workshop looked for commonalties across existing classification systems and tried to link these using broad scale factors important to ecosystem structure and function.

Temporal and spatial aspects of bottlenose dolphin occurrence in coastal and estuarine waters near Charleston, South Carolina

The spatial and temporal occurrence of Atlantic bottlenose dolphins (Tursiops truncatus) in the coastal and estuarine waters near Charleston, SC were evaluated. Sighting and photographic data from photo-identification (ID), remote biopsy, capture-release and radio-tracking studies, conducted from 1994 through 2003, were analyzed in order to further delineate residence patterns of Charleston area bottlenose dolphins. Data from 250 photo-ID, 106 remote biopsy, 15 capture-release and 83 radio-tracking surveys were collected in the Stono River Estuary (n = 247), Charleston Harbor (n = 86), North Edisto River (n = 54), Intracoastal Waterway (n = 26) and the coastal waters north and south of Charleston Harbor (n = 41). Coverage for all survey types was spatially and temporally variable, and in the case of biopsy, capture-release and radio-tracking surveys, data analyzed in this report were collected incidental to other research. Eight-hundred and thirty-nine individuals were photographically identified during the study period. One-hundred and fifteen (13.7%) of the 839 photographically identified individuals were sighted between 11-40 times, evidence of consistent occurrence in the Charleston area (i.e., site fidelity). Adjusted sighting proportions (ASP), which reflect an individual’s sighting frequency in a subarea relative to other subareas after adjusting for survey effort, were analyzed in order to evaluate dolphin spatial occurrence. Forty-three percent (n = 139) of dolphins that qualified for ASP analyses exhibited a strong subarea affiliation while the remaining 57% (n = 187) showed no strong subarea preference. Group size data were derived from field estimates of 2,342 dolphin groups encountered in the five Charleston subareas. Group size appeared positively correlated with degree of “openness” of the body of water where dolphins were encountered; and for sightings along the coast, group size was larger during summer months. This study provides valuable information on the complex nature of bottlenose dolphin spatial and temporal occurrence near Charleston, SC. In addition, it helps us to better understand the stock structure of dolphins along the Atlantic seaboard.