Composition,habitats, seasonal changes and productivity of macroalgae in Grays Harbor Estuary,Washington

Twenty-nine taxa of macroalgae were collected from the Grays Harbor Estuary, Washington, from 17 April 1980 to 4 June 1981. Outer (oceanic) sites contained higher numbers of species than sites located in the inner portion of the estuary. Macroalgae were found in several habitats including attached to boulders, logs, tree roots, other algae, and angiosperms, as mats in sand, and drift.Fucus distichus ssp.edentatus andEnteromorpha intestinalis occurred at the greatest number of sites and were found throughout the year. The standing stock of the perennialFucus remained relatively consant, while that of anE. intestinalis andBlidingia minima var.subsalsa complex showed a significant peak between late spring and early summer as well as a winter minimum. The occurrence of most other taxa was highly seasonal. Net productivity rates for the most abundant macroalgal taxa were moderate to high relative to rates published for algae in other North American estuaries. It is concluded that, although inconspicuous, macroalgae may represent an important contributor of organic carbon to the Grays Harbor estuarine system.     

Formation and seasonal evolution of Atlantic menhaden juvenile nurseries in coastal estuaries

A hypothesis on the formation and seasonal evolution of Atlantic menhaden (Brevoortia tyrannus) juvenile nurseries in coastal estuaries is described. A series of cruises were undertaken to capture postmetamorphic juvenile menhaden and to characterize several biological and physical parameters along estuarine gradients. The two study systems, the Neuse and Pamlico rivers in North Carolina, contain important menhaden nursery grounds. Juvenile menhaden abundance was found to be associated with gradients of phytoplankton biomass as evidenced by chlorophylla levels in the upper water column. Fish abundances were only secondarily associated with salinity gradients as salinity was a factor that moderated primary production in the estuary. The persistence of spatial and temporal trends in the distribution of phytoplankton in the Neuse and Pamlico estuaries was reviewed. The review suggested that postmetamorphic juvenile menhaden modify their distribution patterns to match those created by phytoplankton biomass, which in turn makes them most abundant in the phytoplankton maxima of estuaries. Because the location of these maxima varies with the mixing and nutrient dynamics of different estuaries, so will the location of the nursery.     

Emigration of juvenile Atlantic menhaden,Brevoortia tyrannus (Pisces: Clupeidae), from the York River estuary

The emigration of juvenile Atlantic menhaden,Brevoortia tyrannus (Latrobe), from the York River Estuary, Virginia, was studied during the years 1981 and 1982. Concurrent observations of menhaden catch, water temperature, and phytoplankton abundance suggested that the migration began in response to environmental events in the estuary. Juvenile menhaden appeared to begin their migration five days after the sustained onset of water temperatures below 24 °C. The temperature change was hypothesized as the proximate factor that initiates the migration. Coincident with the migrations, phytoplankton communities in the estuary bloomed, suggesting that the ultimate factor that initiates the migration may be the occurrence of sufficient food for the emigrating menhaden as they moved down and out of the estuary. Migration timing may have evolved as a mechanism to enhance the survival of migrating juvenile menhaden during a period of physiologic stress.     

The distribution of shallow water juvenile fishes in an urban estuary: The effects of manmade structures in the lower Hudson River

The objective of this study was to determine what effect, if any, large pile-supported platforms (piers) have on the habitat distribution and abundance of juvenile fishes. Trapping techniques were used in 1993 and 1994 under piers, in pile fields, and in open-water habitat types in shallow areas (<5 m) in the lower Hudson River estuary (40°44′N, 70°01′W). Nearly 1500 fishes, mostly juveniles, representing 24 species were collected in 1865 trap-days from May through October in the 2-yr study. The presence of relatively large numbers of young-of-the-year (YOY) fish during both years lends support to the idea that shallow areas in the lower Hudson River estuary currently function as nursery habitats for a variety of fishes. Two seasonal assemblages were apparent, but their composition varied somewhat between years.Microgadus tomcod andPseudopleuronectes americanus YOY dominated an early summer assemblage (May–July) while large numbers of YOYMorone saxatilis were collected as part of a late summer assemblage (August–September). The effects of habitat type on fish assemblage structure were significant during both years. Fish abundance and species richness were typically low under piers; YOY fishes were rare andAnguilla rostrata accounted for a large proportion of the total catch. In contrast, YOY fishes dominated collections at pile field and open-water stations, where abundance and species richness were high. These results indicate that habitat quality under the platforms of large piers (>20,000 m²) is probably poor for YOY fishes when compared with nearby pile field and open-water habitat types.     

Spatio-temporal fluctuations in the distribution and abundance of demersal fish and epibenthic crustaceans in Yaquina Bay,Oregon

A total of over 32,000 demersal fish and epibenthic crustaceans belonging to 62 species were caught in 42 biweekly trawls from 10 stations in Yaquina Bay, Oregon, during 1967 and 1968. English sole,Parophrys vetulus, was the most abundant species. Seventeen species (13 fishes and 4 crustaceans) constituted 95% of the catch. Total numerical abundances of both individuals (mainly juvenile fishes) and species were greatest in the lower 12 km of the estuary during summer and early fall, a period of water mass stability and increased water temperature and salinity. This section of the estuary is used by many immature fishes and crustaceans as a “nursery area”. These fishes generally emigrate from the estuary as subadults in the fall around the onset of the rainy season. The fewest species were taken in January 1968 from the central, upper-estuarine, and riverine areas of the bay, this being a time when high rainfall and river discharge result in low salinity and temperature. Crustaceans (shrimp and subadult crabs) were generally most abundant in late winter and early spring throughout the estuary. Changes in diversity indices reflected variations in community structure, the influence of migratory species and juvenile fishes, and seasonal changes in dominance. Year-to-year fluctuations in abundance may be due, in part, to local hydrographic and meteorological conditions along the central Oregon coast.     

Stock-Specific Movement and Distribution of Juvenile Chinook Salmon, <Emphasis Type="Italic">Oncorhynchus tshawytscha</Emphasis>, in Sandy Beach Surf Zones of Oregon and Washington,USA

Sandy beach surf zones serve as alternative nursery habitats for juvenile Chinook salmon (0 age) during their early marine residency, a period considered critical due to high and variable mortality rates. Despite the importance of early marine residence, the extent of juvenile salmon surf zone use and movement along sandy beaches is not well understood. Juvenile Chinook salmon distribution and movement were studied in shallow surf zone habitats by sampling from 2006 to 2010 with a beach seine 11 beaches adjacent and distant to four estuary mouths in Oregon and Washington, USA. The estuary of origin of each juvenile was determined using genetic stock identification methods and coded wire tags. Surf zones sampled were within littoral cells, which are stretches of the coastline bordered by rocky headlands, and included estuaries with and without Chinook salmon populations. Juvenile salmonids were only collected at littoral cells with Chinook-inhabited watersheds. Most juveniles (95 %) were present at sandy beaches adjacent (<500 m from estuary mouth) to their estuary of origin. Few Chinook salmon (5 %) were collected at littoral cells that contained non-natal estuaries. These results indicate that juvenile Chinook salmon inhabiting surf zones mostly use beaches adjacent to their estuaries of origin, but some juveniles may reside in beaches distant from their point of ocean entry.     

Causes of interestuarine variability in bay anchovy (<Emphasis Type="Italic">Anchoa mitchilli</Emphasis>) salinity at capture

Salinities occupied by different life stages of bay anchovy (Anchoa mitchilli) were compared over annual cycles at 128 stations in 12 Florida estuaries. The comparison included eight stations in an oligotrophic, groundwater-based estuary in which all life stages were rare or absent. At other stations, adults, eggs, and early larvae occurred in intermediate to high salinities (10-30 psu) with no apparent central salinity tendency. The larva-juvenile transition was marked by an upstream shift to lower salinities (0-15 psu), also with no central salinity tendency. Mean salinities of the juvenile catch were strongly dependent on the salinities of the sampling effort. This dependence was strongest in estuaries that had weak horizontal salinity gradients. Weak salinity gradients were either natural or resulted from estuarine dams. After using nonlinear regression to account for the interaction between effort salinity and catch salinity, catch salinities were found to be similar from year to year within estuaries, but widely different among estuaries, with interestuarine differences ranging as high as 10–13 psu. Lower salinities were occupied by juveniles in estuaries that had long freshwater turnover times. Inherent geomorphic and inflow-related effects on the distribution of prey resources, coupled with an ontogenetic diet shift, are proposed as the explanation for both the habitat shift and the strong interestuarine variability in salinity at capture.     

Seasonal and spatial distribution of planktonic crustacea in the lower Saint John River,a multibasin estuary in New Brunswick,Canada

Five stations on the lower Saint John River, a complex multibasin estuary, were sampled semiquantitatively for zooplankton at biweekly intervals for one year, and qualitatively over a 4-year period. Planktonic Crustacea were dominated by the true estuarine copepods,Acartia tonsa andEurytemora affinis and the euryhaline marine copepodsOithona similis andPseudocalanus minutus. Atypical estuarine forms, confined to a lower fiord-like basin with salinity of 20‰, were the amphipod,Parathemisto abyssorum and the mysidErythrops erythrophthalma. River flows were highly variable from year to year. Certain basins function as lakes in some years and estuaries in other years, causing extreme zooplankton community fluctuations, and succession patterns dependent on salinity rather than season. On occasion freshwater zooplankters maintained viable populations at unusually high salinities (ca. 5‰). Vertical and horizontal distributions of zooplankters indicate that the estuary in fact comprises two systems: a true estuary in the upper reaches and the surface waters at the lower end, and a fiord in a subsidiary basin in the lower end.     

Application of the concentration hypothesis to English sole in nursery estuaries and potential contribution to coastal fisheries

Resources in nursery areas can be important determinants of recruitment for juvenile fishes. Most young-of-the-year English sole (Pleuronectes vetulus) appear to rely on estuaries on the U.S. Pacific Northwest coast as nursery areas. Trawl surveys were conducted in four nursery estuaries, and the results show consistent densities were found across all estuaries in August. In June densities were higher and more variable. Application of the average August density to estuaries along the entire Oregon and Washington coasts resulted in an estimated total estuarine abundance of 45.8 million age 0+ English sole. Estimated coast-wide recruitment of age 4+ female English sole based on age 0+ abundance ranged from 3.7 to 4.9 million individuals from 1998–2000, with an average value of 4.3 million. A simple population model was constructed to determine if production from the combined Oregon and Washington estuaries was consistent with the estimates of the adult stock, and the observed catch from 1956–1997. The observed commercial catch has declined over this time period, and the trend could be fit using an availability-gear efficiency of 21% and an exploitation rate of 0.094. The results suggest that the English sole population on the Oregon-Washington shelf could potentially be supported solely by estuarine production, and this production appears to be stabilized by the size of available nursery areas.     

Distribution of Winter Flounder, Pseudopleuronectes americanus, in the Hampton–Seabrook Estuary, New Hampshire: Observations from a Field Study

From July to October 2004, five sites in the Hampton–Seabrook Estuary in New Hampshire were sampled with beam and otter trawls. The goals were to describe winter flounder (1) abundance in the estuary, (2) size class distributions, (3) spatial distribution by different size classes, and (4) distribution patterns. Of the 19 species caught, winter flounder was the most abundant and was dominated by young-of-the-year (YOY) fish. The five sites were fairly homogenous in depth, bottom type, salinity, and temperature. However, YOY abundance ranged from 2.1 to 32.1 fish 1,000 m^?2 depending on the site. Benthic community was the best indicator of juvenile winter flounder abundance. Catch data of other organisms fluctuated, but no one species was a strong predictor of winter flounder abundance and distribution. During late summer and early fall, the estuary is used primarily by YOY winter flounder, indicating that this estuary functions as a nursery ground.     

Patterns in use of estuarine habitat by juvenile English sole (Pleuronectes vetulus) in four Eastern North Pacific estuaries

English sole (Pleuronectes vetulus) is one of a few commercially important marine fishes on the Pacific coast of North America that use estuarine areas as nurseries for juvenile stages. Trawl surveys of four United States Pacific Northwest estuaries were conducted to determine spatial patterns of juvenile English sole residence in estuaries during 1998–2000. Additional data from 1983–1988 were also analyzed. Two size classes of juvenile English sole were identified during surveys, with densities of small (Total length [TL] <50 mm) sole ranging from 0 to 11,300 fish ha^?1 across all sites, and densities of large (TL 50–150 mm) sole ranging from 0 to 33,000 fish ha^?1 across all sites. Principal components analysis of static habitat data collected at each trawl survey site was used to define habitat types within each estuary, and discriminant function analysis was used to test the resulting classification scheme. Both small and large cohort English sole used lower side channel locations at significantly higher densities than other estuarine areas. Small English sole also showed significant relationships with both bottom temperature and depth. These patterns in habitat use were consistent across all estuaries and indicate that English sole used shallow depth areas surrounded by extensive tidal flats, where temperatures were optimal for growth. The analysis also suggested a carrying capacity may exist for large English sole in nursery estuaries.     

Distribution and abundance patterns of flatfishes in the Sado estuary, Portugal

The flatfish community of the Sado estuary was studied based on beam trawl catches in six sampling areas. Temperature and salinity were recorded during surveys and sediment composition was determined at each sampling area. A total of 12 species were identified (1 Bothidae, 1 Pleuronectidae, and 10 Soleidae).Dicologoglossa hexophthalma (Bennett 1831),Microchirus ocellatus (Linnaeus 1758), andSynaptura lusitanica (Capello 1868) were new records to this estuarine system.Monochirus hispidus Rafinesque, 1814, was the most abundant species (about 80% of the total individuals caught). Community structure reflected both spatial and temporal patterns. A longitudinal abundance pattern was noticed with some species much more abundant in outer estuarine areas, namelyM. hispidus, Arnoglossus laterna (Walbaum 1792), andBuglossidium luteum (Risso 1810), while others, such asSolea solea (Linnaeus 1758) andSolea senegalensis Kaup, 1858, presented the highest densities in inner areas. Besides temperature and salinity gradients, species distribution was also influenced by sediment composition. Seasonal variation was mainly determined by the different periods of juvenile peak abundance according to the species which emphasize the role of the estuary as a nursery ground for several flatfish species.     

Direct and Indirect Interactions Between Lower Estuarine Mangrove and Saltmarsh Habitats and a Commercially Important Penaeid Shrimp

Vegetated habitats in estuaries may provide a structural refuge and food supply in the same place, but benefits are also derived where a productive food source and suitable habitat are adjacent to each other. Quantifying these relationships is fundamental to understanding the structural and functional characteristics of estuarine ecosystems and for informing management actions. Effective juvenile habitat (habitat that contributes greater-than-average numbers of recruits to the adult population), recruitment patterns and trophic relationships were studied for Eastern King Prawn (Penaeus plebejus) in the lower Clarence River estuary, New South Wales, between 2014 and 2016. Effective juvenile habitat was identified in both the north arm and main river channel of the estuary, and these areas also supported a higher abundance of juvenile prawns. There was minimal recruitment to the southern channels of the estuary, possibly due to reduced connectivity with the incoming tide arising from a rock wall. Trophic relationships in parts of the lower estuary were evaluated using stable isotopes, and saltmarsh grass (Sporobolus virginicus) was the dominant primary producer supporting juvenile Eastern King Prawn productivity across the area. Mangroves were of minimal importance, and seagrass cover was minimal in the area studied. The patterns observed indicate that nursery function of different areas within the lower estuary is a product of connectivity, recruitment and nutrition derived from primary productivity of vascular plants. Habitats within the lower Clarence River estuary have seen substantial degradation over decadal time scales, and the implications of our findings for targeting future habitat repair are discussed.     

Growth of juvenile spot,Leiostomus xanthurus Lacépède,in the nursery region of the James River,Virginia

Thein situ growth of juvenile spot,Leiostomus xanthurus Lacépède, was investigated in a nursery area of the James River, Virginia. Juvenile growth was fairly rapid (11.34 mm standard length per month) during their first spring and summer in the nursery grounds, and leveled off in the autumn. The mean size of spot after the first year was calculated to be 148 mm standard length. The weight-length relationship was log₁₀W = ?5.018+3.246 (log₁₀L), where W = wet weight in grams and L = standard length in millimeters. The weight-length relationship of juvenile spot of the James River estuary differed statistically from that reported from South Carolina, Mississippi, Louisiana, and Texas. Spot of the James River, Virginia, were found to be heavier per unit length than those of other regions, which suggests that the Chesapeake Bay system provides an optimum environment for growth of 0-year class fish.     

Long-term patterns in the diets of Japanese temperate bassLateolabrax japonicus larvae and juveniles in Chikugo estuarine nursery ground in Ariake Bay, Japan

Larval and juvenile Japanese temperate bass (Lateolabrax japonicus) samples were collected from a wide range of spatial gradients (covering a distance of approximately 30 km) in Chikugo estuary, Ariake Bay, Japan over a period of 8 yr (1997–2004) in order to observe changes in diet. Gut contents were studied by separating, identifying, counting, and estimating the dry weight of prey organisms. Copepod samples were collected during each cruise to observe the numerical composition, abundance, and biomass in the estuary. Considerable spatial and temporal variations were observed in copepod distributions in ambient water and the diets of the fish. Two distinctly different copepod assemblages were identified in the estuary: One in the upper estuarine turbidity maximum (ETM), dominated by a single speciesSinocalanus sinensis and the other in the lower estuary consisting of a multispecies assemblage, dominated byOithona davisae, Acartia omorii, Paracalanus parvus, andCalanus sinicus. The gut content composition of the fish in the upper estuary was dominated byS. sinensis, while in the lower estuary, it consisted ofP. parvus, O. davisae, andA. omorii. Within the size group analyzed (13.0–27.0 mm SL), the smaller individuals were found to feed on a mixed diet composed of smaller prey. The diets gradually shifted to bigger prey composed predominantly ofS. sinensis for larger size groups. Greater proportions of empty guts were recorded in the smaller individuals and dropped with increasing fish size. Higher dry biomass of copepods in the environment, as well as higher dry weights of gut contents, were recorded in the upper estuary, indicating that the upper estuarine ETM areas are important nursery grounds for the early life stages of the Japanese temperate bass. The early life stages of the Japanese temperate bass are adapted to use the upstream nursery grounds and ascending to the nursery areas to useS. sinensis is one of the key survival strategies of the Japanese temperate bass in the Chikugo estuary.     

Presence of Fish on the Shallow Flooded Margins of a Small Intermittently Open Estuary in South Eastern Australia under Variable Flooding Regimes

Shallow water habitats within estuarine systems are believed to be important areas for small fish. While a wide variety of shallow habitats have been studied, the land that becomes inundated by the damming effect after the closure of intermittently open mouths has previously been overlooked. Fish were sampled monthly from both the main channel and flood zone of an intermittently open estuary between July 2004 and June 2005 using minifyke nets during the day and at night. A total of 7,787 fish were collected during the study representing 13 species and 11 families. Philypnodon grandiceps was the most abundant species and, together with Atherinosoma microstoma, Pseudogobius olorum, and Galaxias maculatus, made up 94% of the total catch. Inundation of the flood zone occurred in two discrete forms associated with mouth condition, which consisted of sporadic flooding while the mouth was open, to long-term flooding for 6 months after its closure. Large numbers of fish were captured on the flood zone, which included nine species; however, A. microstoma dominated the catch. A distinct shift in the flood zone fish assemblage occurred between the two mouth conditions, which is likely associated with changes in hydro-period and food availability of the flood zone and physico-chemical parameters in the main channel. There was no longitudinal variation in the fish assemblage in both the main channel and flood zone; similarly, the diel period was found to have little effect on the fish assemblage. The total catch per unit effort did not vary across seasons and suggests that fish abundance within the estuary is stable throughout the year. Unlike other estuarine systems where shallow water fish assemblages may be structured by variations in tide and elevation within the Surrey, freshwater inflow and, more importantly, mouth condition appear to have the greatest influence in composition of the shallow water flood zone fish assemblage of intermittently open estuaries.     

Notes on the occurrence,distribution, and biology of elasmobranch fishes in the Indian River lagoon system,Florida

Fifteen species of elasmobranchs, eight sharks and seven rays, have been recorded with reasonable certainty from the Indian River lagoon system on the central east coast of Florida. We collected four shark and six ray species during a three and one-half year study of the northern portion of the lagoon system. Five of these appear to be year-round residents, and the remainder utilize the area only at restricted times of the year or as a nursery ground. The most abundant resident species areDasyatis sayi, D. sabina, andCarcharhinus leucas. Pristis pectinata, once a common resident species, has been extirpated from the lagoons. The distribution of ocean inlets and salinity appear to be major factors affecting diversity and numbers of elasmobranchs in the Indian River system.     

Diel Variation in the Pelagic Fish Assemblage in a Temperate Estuary

The pelagic fish assemblage within a temperate estuary was examined to determine if there were diel differences in species richness, total abundance, biomass, and species composition. These comparisons were made over both seasonal (January–December 1996) and annual (August–November 1995; August–December 1996) scales with pop net collections in a shallow (<2 m MLW) embayment within Great Bay in southern New Jersey, USA. In the complete year of sampling in 1996, more than 335,000 pelagic fish, representing 13 families (23 species), were collected during diel sampling with 12 species constituting over 99.9% of the total catch including Clupea harengus (84%), Menidia menidia (10%), and Anchoa mitchilli (4%). A detailed examination determined that nighttime species richness, total abundance and biomass may have been enhanced during some seasons by using artificial light. Diel variation in species composition was similar regardless of the use of the artificial light in all seasons but fall. Annual comparisons between 1995 and 1996 during late summer and fall found these results to be consistent. In general, these findings point out the importance of sampling during both day and night to understand the movement and abundance patterns of estuarine pelagic fishes and their ecological significance in temperate estuaries.     

Seasonal succession and breeding cycles of three species of Acartia (Copepoda: Calanoida) in a maine estuary

Seasonal succession of three species of Acartia in a Maine estuary was examined. The well-defined successional pattern, in which A. tonsa is replaced, by A. clausi in winter and early spring, is well-documented in the middle Atlantic estuaries, but was not observed in this northern New England estuary. Instead, both species increased in their abundance at the same time on most occasions. In general, A. clausi was present throughout the year and produced three generations from March to November. A. longiremis had two or three generations between May and November, and disappeared during late summer. A. tonsa was present from May through December and was most abundant in early fall. A. clausi and A. tonsa were generally most numerous upstream, and A. longiremis downstream. Adult and copepodite V sex ratios varied among species, stations, and seasons. Seasonal patterns of Acartia populations in estuaries of the north Atlantic coast and their possible relationships to environmental factors were also compared and discussed.     

Can Saltwater Intrusion Affect a Phytoplankton Community and Its Net Primary Production? A Study Based on Satellite and Field Observations

Net primary production (NPP) by phytoplankton is a crucial regulator of the carbon cycle and other biological processes in estuaries. Under the impacts of rising sea levels, most estuaries are experiencing increased saltwater intrusion. To determine how these changes in intrusion affect phytoplankton communities and their NPP, a study was performed in the Pearl River Estuary (PRE), China. The results based on monthly global ocean NPP satellite products from 2003 to 2015 show that NPP generally decreased from the north (the upper outlet) to the south (the estuary mouth) in the PRE, whereas temporally, NPP in the rainy season (April to September) exhibited an inverted V-shaped curve, with a maximum value in July and was generally higher than that in the dry season (October to the following March). Field observations of salinity increased from north to south in the PRE, but phytoplankton species and cell numbers decreased from outlets toward the outer estuary. Further analysis showed that NPP and phytoplankton species were positively correlated (R²?~?0.5), whereas NPP and salinity were negatively correlated (R²?~?0.4). Overall, saltwater intrusion in the dry season increased salinity and changed the phytoplankton species abundance and composition, and it may inhibit phytoplankton growth, thereby decreasing NPP.