Adrian Jordaan

Centuries of Anadromous Forage Fish Loss: Consequences for Ecosystem Connectivity and Productivity

Lost biomass of anadromous forage species resulting from the seventeenth to nineteenth century damming of waterways and from overharvest in the northeastern United States contributed to significant changes in coastal marine—terrestrial ecosystems. Historic alewife populations in Maine for the years 1600–1900 were assessed using analyses of nineteenth and twentieth century harvest records and waterway obstruction records dating to the 1600s. Obstructed spawning access in nine watersheds reduced the annual alewife productivity per watershed to 0%–16% of virgin estimates, equaling a cumulative lost fisheries production of 11 billion fish from 1750 to 1900. Including preharvest production, our estimates suggest a lost flux of anadromous forage fish increasing from 10 million fish per year in 1700 to 1.4 billion annually by 1850. Our results suggest a realignment of current restoration goals is needed to recognize oceanic and freshwater ecosystem interdependence and the gap between current targets and potential productivity.

Genetic mixed‐stock analysis of Atlantic sturgeon Acipenser oxyrinchus oxyrinchus in a heavily exploited marine habitat indicates the need for routine genetic monitoring

Although a previous genetic mixed-stock analysis (gMSA) conducted in the early 1990s showed that marine-captured New York Bight Atlantic sturgeon Acipenser oxyrinchus oxyrinchus almost exclusively originated from the Hudson River, fish from southern U.S. rivers were well represented within this contemporary sample (n = 364 fish), at least during the autumn. Widely distributed spawning stocks are therefore exposed to heavy fishing activity and habitat degradation in this relatively small area, illustrating the need for spatial management across multiple management jurisdictions and routine gMSA to account for temporal change.

Recruitment Patterns and Habitat Use of Young-of-the-Year Bluefish along the United States East Coast: Insights from Coordinated Coastwide Sampling

Protracted spawning and pulsed juvenile production are common in coastal spawning fishes, the phenology of which determines potential environmental effects on recruitment. This article examines bluefish (Pomatomus saltatrix), a cosmopolitan coastal spawning species that produces multiple cohorts of juveniles utilizing both estuarine and coastal habitats as nurseries along the U.S. east coast. To determine recruitment on a coastwide basis, ocean (bottom, neuston, and surfzone) and estuarine habitats were sampled in Florida and North Carolina south of Cape Hatteras in the South Atlantic Bight, and Maryland, New Jersey, and New York in the Middle Atlantic Bight. This coordinated sampling effort across multiple habitats with multiple gears on a coastwide basis allowed the resolution of the occurrence, growth, and movement of cohorts along the coast. Production of the spring-spawned cohort occurred in both South Atlantic Bight and Middle Atlantic Bight habitats, while summer-spawned cohort production was limited to the Middle Atlantic Bight. Information from the present study is synthesized with prior research to develop a conceptual model of the seasonal patterns of YOY bluefish habitat use and to emphasize the value of coordinated sampling at a large spatial scale in understanding recruitment processes in this and potentially other important marine species.

Marine Distribution and Habitat Use of Atlantic Sturgeon in New York Lead to Fisheries Interactions and Bycatch

Abstract Population declines of Atlantic Sturgeon Acipenser oxyrinchus oxyrinchus prompted initial fisheries closures and an eventual endangered or threatened species listing across the U.S. portion of their range in 2012. Atlantic Sturgeon aggregations and migration routes along the coast of Long Island overlap with commercial fishing activities that may lead to incidental take in nondirected fisheries. Thus, understanding the distribution and movement of Atlantic Sturgeon in relation to commercial fisheries can help management agencies determine impacts and develop bycatch mitigation measures. Stratified random sampling and targeted bottom trawl surveys were used to identify the temporal and spatial use of marine habitat in New York waters. The majority of survey captures were restricted to depths of less than 15 m and known aggregation areas. During the aggregation periods (May, June, September, and October) in known aggregation areas, catches were an order of magnitude higher than in other areas and months of the year. Northeast Fisheries Observer Program bycatch data from 1989 to 2013 was analyzed for the New York region and suggested that bycatch occurs within two main gear types: otter bottom trawls and sink gill nets. Trawling bycatch contained primarily subadult Atlantic Sturgeon and is highest during the Summer Flounder Paralichthys dentatus fishery in New York State waters. Trawling overlaps spatially and temporally with identified Atlantic Sturgeon aggregation areas, while bycatch in gill nets targeted adult fish farther offshore in federal waters. Bycatch in these fisheries may be a regional threat to recovery, and spatial and temporal closures, gear modifications, or other bycatch reduction techniques are suggested to protect aggregating and migrating fish.

Dynamic seascapes predict the marine occurrence of an endangered species: Atlantic Sturgeon Acipenser oxyrinchus oxyrinchus

Summary Categorical landscapes are powerful environmental partitions that index complex biogeochemical processes that drive terrestrial species distributions. However, translating landscapes into seascapes requires that the dynamic nature of the fluid environment be reflected in spatial and temporal boundaries such that seascapes can be used in marine species distribution models and conservation decisions. A seascape product derived from satellite ocean colour and sea surface temperature partitioned mid-Atlantic coastal waters on scales commensurate with the Atlantic Sturgeon migration. The seascapes were then matched with acoustic telemetry records of Atlantic Sturgeon to determine seascape selectivity. To test for selectivity, we used real-time satellite seascape maps to normalize the sampling of an autonomous underwater vehicle that resampled similar geographic regions with time varying seascape classifications. Our findings suggest that Atlantic Sturgeon prefer one seascape class over those available in the coastal ocean, indicating selection for covarying environmental properties rather than geographical location. The recent listing of Atlantic Sturgeon as Endangered throughout much of their United States range has highlighted the need for improved understanding of marine habitat requirements to reduce interactions with anthropogenic stressors. Narrow dynamic migration corridors may enable seascapes to be used as a daily decision tool by industry and managers to reduce interactions with this imperilled species during coastal migrations.

Biology and Ecology of Long Island Sound

Many compelling management issues in Long Island Sound (LIS) focus on how organisms respond to stresses such as commercial and recreational harvesting, eutrophication, hypoxia, habitat degradation, invasion of non-native species, ocean acidification, and climate change. In order to address these complex problems, we must first understand the factors controlling biological processes and how organisms interact ecologically. This chapter provides an overview of the major groups of organisms occupying the dominant habitats of LIS.

Fish assemblages spatially structure along a multi-scale wave energy gradient

Elucidating how ecological systems structure along environmental gradients to form barriers is important for improving the understanding of community ecology and the management of human-nature interactions (fisheries). Principal Component Analysis was used to create new variables from species abundance data collected in a seine survey on the Maine coast. The new variables were related to wave-energy values created for each site from available wind speed and fetch data. The results show a strong relationship between potential wave energy experienced and the species composition at a location. There were two scales of importance in determining species assemblages. First is at the regional scale where wave energy and the resulting coastal geomorphology create barriers to certain species and act to maintain different species groups. Second is at the local scale where wave energy interacts with species traits to create differences in species assemblages within a specific bay. The structure in fish communities delineated through this analysis provides a biodiversity indicator and the relationship between this indicator and an easily estimated physical quantity allows area-based management concepts to be better designed. For example, essential habitats of one or many species may be inferred through analysis of available environmental data, rather than depending on costly and time-consuming surveys of entire regions.

Linkages among physical and biological properties in tidepools on the Maine Coast

Tidepools experience significant gradients in ecologically relevant physical variables along the transition from ocean to terrestrial habitat (vertical axis) and from open coast to inner bays (horizontal axis). Associations amongst physical and biological variables, divided into algal, invertebrate and vertebrate (fish) groups, were examined in a tidepool survey dataset. Physical variables and the three biological groups were submitted separately to a principal component analysis (PCA). PCA scores were evaluated with Pearson correlation coefficients across the sampling units (tidepools) to identify significant correlations. Initially little structure in the data and no correlation amongst variables was present. At the onset of summer, correlations were confined amongst physical variables and algal and invertebrate components, followed in the late summer with correlations between invertebrate and fish components. By the fall, correlations were confined to fish and algal/invertebrate components. Species relationships followed a seasonal cycle with a succession from little to no structure, the forming of low trophic level relationships in the early summer to high trophic level relationships in late summer-fall, and deconstruction of structure with the onset of fall-winter storms and ice scour. The seasonal pattern, and well established vertical gradient, has nested within it species composition changes along a horizontal wave energy gradient. The horizontal gradient results in a shift from species which are physiologically adapted to extreme salinities and temperatures to those which are physically adapted to high wave-energy environments.

Growth and Mortality in Coastal Populations of Winter Flounder: Implications for Recovery of a Depleted Population

Abstract We studied growth, mortality, and settlement distributions of juvenile Winter Flounder Pseudopleuronectes americanus in two bays of Long Island, New York, to better understand localized population dynamics of a species experiencing a protracted population decline. Juvenile mortality in Long Island bays ranged between 0.02 and 0.04 per day and was as high as or higher than values reported for other systems. Settlement distributions had multiple peaks (cohorts) occurring between March and late July in 2007 and between February and May in 2008. The presence of multiple cohorts limited the usefulness of field-derived, length-based estimates of growth, resulting in unrealistic values compared with otolith-based measures (field based: -0.05 to 0.25 cm/d; otolith based: 0.05–0.06 cm/d). Thus, we recommend the use of otolith methods or the repeated measurement of individuals to estimate growth of juvenile Winter Flounder. Otolith-based growth rate was significantly higher for Port Jefferson Harbor during 2007 than for all other year × location combinations. Together with previous research showing genetic differentiation and migratory diversity, our finding of multiple spawning cohorts in Long Island Winter Flounder suggests a degree of isolation, and local management will be needed to support healthy populations. Future research to determine adult spawning, migratory behavior, stock structure, duration of the larval period, and settlement timing is required to unravel the complex behavior of Winter Flounder.

Temporal Patterns of Migration and Spawning of River Herring in Coastal Massachusetts

AbstractMigrations of springtime Alewife Alosa pseudoharengus and Blueback Herring A. aestivalis, collectively referred to as river herring, are monitored in many rivers along the Atlantic coast to estimate population sizes. While these estimates give an indication of annual differences in the number of returning adults, links to the subsequent timing and duration of spawning and freshwater juvenile productivity remain equivocal. In this study, we captured juvenile river herring at night in 20 coastal Massachusetts lakes using a purse seine and extracted otoliths to derive daily fish ages and back-calculate spawn dates. Estimates of spawning dates were compared with fishway counts of migrating adults to assess differences in migration timing and the timing and duration of spawning. We observed a distinct delay between the beginning of the adult migration run and the start of spawning, ranging from 7 to 28 d across the 20 lakes. Spawning continued 13–48 d after adults stopped migrating into freshwater, fur...