Habitat and diet overlap of 4 piscivorous fishes: variation on the inner continental shelf off New Jersey

Piscivorous fishes, many of which are economically valuable, play an important role in marine ecosystems and have the potential to affect fish and invertebrate populations at lower trophic levels. Therefore, a quantitative understanding of the foraging ecology of piscivores is needed for ecosystem-based fishery management plans to be successful. Abundance and stomach contents of seasonally co-occurring piscivores were examined to determine overlap in resource use for Summer Flounder (Paralichthys dentatus; 206–670 mm total length [TL]), Weakfish (Cynoscion regalis; 80–565 mm TL), Bluefish (Pomatomus saltatrix; 55–732 mm fork length [FL]), and Striped Bass (Morone saxatilis; 422–920 mm FL). We collected samples from monthly, fishery-independent trawl surveys conducted on the inner continental shelf (5–27 m) off New Jersey from June to October 2005. Fish abundances and overlaps in diet and habitat varied over this study period. A wide range of fish and invertebrate prey was consumed by each species. Diet composition (determined from 1997 stomachs with identifiable contents) varied with ontogeny (size) and indicated limited overlap between most of the species size classes examined. Although many prey categories were shared by the piscivores examined, different temporal and spatial patterns in habitat use seemed to alleviate potential competition for prey. Nevertheless, the degree of overlap in both fish distributions and diets increased severalfold in the fall as species left estuaries and migrated across and along the study area. Therefore, the transitional period of fall migration, when fish densities are higher than at other times of the year, may be critical for unraveling resource overlap for these seasonally migrant predators.

The potential consequences of climate variability and change on coastal areas and marine resources: report of the Coastal Areas and Marine Resources Sector Team, U.S. National Assessment of the Potential Consequences of Climate Variability and Change, U.S. Global Change Research Program

Coastal and marine ecosystems support diverse and important fisheries throughout the nation’s waters, hold vast storehouses of biological diversity, and provide unparalleled recreational opportunities. Some 53% of the total U.S. population live on the 17% of land in the coastal zone, and these areas become more crowded every year. Demands on coastal and marine resources are rapidly increasing, and as coastal areas become more developed, the vulnerability of human settlements to hurricanes, storm surges, and flooding events also increases. Coastal and marine environments are intrinsically linked to climate in many ways. The ocean is an important distributor of the planet’s heat, and this distribution could be strongly influenced by changes in global climate over the 21st century. Sea-level rise is projected to accelerate during the 21st century, with dramatic impacts in low-lying regions where subsidence and erosion problems already exist. Many other impacts of climate change on the oceans are difficult to project, such as the effects on ocean temperatures and precipitation patterns, although the potential consequences of various changes can be assessed to a degree. In other instances, research is demonstrating that global changes may already be significantly impacting marine ecosystems, such as the impact of increasing nitrogen on coastal waters and the direct effect of increasing carbon dioxide on coral reefs. Coastal erosion is already a widespread problem in much of the country and has significant impacts on undeveloped shorelines as well as on coastal development and infrastructure. Along the Pacific Coast, cycles of beach and cliff erosion have been linked to El Niño events that elevate average sea levels over the short term and alter storm tracks that affect erosion and wave damage along the coastline. These impacts will be exacerbated by long-term sea-level rise. Atlantic and Gulf coastlines are especially vulnerable to long-term sea-level rise as well as any increase in the frequency of storm surges or hurricanes. Most erosion events here are the result of storms and extreme events, and the slope of these areas is so gentle that a small rise in sea level produces a large inland shift of the shoreline. When buildings, roads and seawalls block this natural migration, the beaches and shorelines erode, threatening property and infrastructure as well as coastal ecosystems.

Flux and sources of nutrients in the Mississippi-Atchafalaya River Basin: Topic 3 Report for the Integrated Assessment on Hypoxia in the Gulf of Mexico.

Ths report addresses the following two questions: 1) What are the loads (flux) of nutrients transported from the Mississippi-Atchafalaya River Basin to the Gulf of Mexico, and where do they come from within the basin? 2) What is the relative importance of specific human activities, such as agriculture, point-source discharges, and atmospheric deposition in contributing to these loads? These questions were addressed by first estimating the flux of nutrients from the Mississippi-Atchafalaya River Basin and about 50 interior basins in the Mississippi River system using measured historical streamflow and water quality data. Annual nutrient inputs and outputs to each basin were estimated using data from the National Agricultural Statistics Service, National Atmospheric Deposition Program, and point-source data provided by the USEPA. Next, a nitrogen mass balance was developed using agricultural statistics, estimates of nutrient cycling in agricultural systems, and a geographic information system. Finally, multiple regression models were developed to estimate the relative contributions of the major input sources to the flux of nitrogen and phosphorus to the Gulf of Mexico.

Harmful algal blooms in coastal waters: options for prevention, control and mitigation

This report is the product of a panel of experts in the science of blooms of unicellular marine algae which can cause mass mortalities in a variety of marine organisms and cause illness and even death in humans who consume contaminated seafood. These phenomena are collectively termed harmful algal blooms or HABs for short. As a counterpart to recent assessments of the priorities for scientific research to understand the causes and behavior of HABs, this assessment addressed the management options for reducing their incidence and extent (prevention), actions that can quell or contain blooms (control), and steps to reduce the losses of resources or economic values and minimize human health risks (mitigation). This assessment is limited to an appraisal of scientific understanding, but also reflects consideration of information and perspectives provided by regional experts, agency managers and user constituencies during three regional meetings. The panel convened these meetings during the latter half of 1996 to solicit information and opinions from scientific experts, agency managers and user constituencies in Texas, Washington, and Florida. The panel's assessment limited its attention to those HABs that result in neurotoxic shellfish poisoning, paralytic shellfish poisoning, brown tides, amnesic shellfish poisoning, and aquaculture fish kills. This covers most, but certainly not all, HAB problems in the U.S.

Ecological Condition of Coastal Ocean Waters within Stellwagen Bank National Marine Sanctuary: 2008

In June 2008, the NOAA National Ocean Service (NOS), in conjunction with the EPA National Health and Environmental Effects Laboratory (NHEERL), conducted an assessment of the status of ecological condition of soft-bottom habitat and overlying waters within the boundaries of Stellwagen Bank National Marine Sanctuary (SBNMS). The sanctuary lies approximately 20 nautical miles east of Boston, MA in the southwest Gulf of Maine between Cape Ann and Cape Cod and encompassing 638 square nautical miles (2,181 km2). A total of 30 stations were targeted for sampling using standard methods and indicators applied in prior NOAA coastal studies and EPA’s Environmental Monitoring and Assessment Program (EMAP) and National Coastal Assessment (NCA). A key feature adopted from these studies was the incorporation of a random probabilistic sampling design. Such a design provides a basis for making unbiased statistical estimates of the spatial extent of ecological condition relative to various measured indicators and corresponding thresholds of concern. Indicators included multiple measures of water quality, sediment quality, and biological condition (benthic fauna, fish tissue contaminant levels). Depths ranged from 31 – 137 m throughout the study area. About 76 % of the area had sediments composed of sands (< 20 % silt-clay), 17 % of the area was composed of intermediate muddy sands (20 – 80 % silt-clay), and 7 % of the sampled area consisted of mud (> 80 % siltclay). About 70 % of the area (represented by 21 sites) had sediment total organic carbon (TOC) concentrations < 5 mg/g and all but one site (located in Stellwagen Basin) had levels of TOC < 20 mg/g, which is well below the range potentially harmful to benthic fauna (> 50 mg/g). Surface salinities ranged from 30.6 – 31.5 psu, with the majority of the study region (approximately 80 % of the area) having surface salinities between 30.8 and 31.4 psu. Bottom salinities varied between 32.1 and 32.5 psu, with bottom salinities at all sites having values above the range of surface salinities. Surface-water temperatures varied between 12.1 and 16.8 ºC, while near-bottom waters ranged in temperature from 4.4 – 6.2 ºC. An index of density stratification (Δσt) indicated that the waters of SBNMS were stratified at the time of sampling. Values of Δσt at 29 of the 30 sites sampled in this study (96.7 % of the study area) varied from 2.1 – 3.2, which is within the range considered to be indicative of strong vertical stratification (Δσt > 2) and typical of the western Gulf of Maine in summer. Levels of dissolved oxygen (DO) were confined to a fairly narrow range in surface (8.8 – 10.4 mg/L) and bottom (8.5 – 9.6 mg/L) waters throughout the survey area. These levels are within the range considered indicative of good water quality (> 5 mg/L) with respect to DO. None of these waters had DO at low levels (< 2 mg/L) potentially harmful to benthic fauna and fish.

Sources of age determination errors for sablefish (Anoplopoma fimbria)

This study was undertaken to resolve problems in age determination of sablefish (Anoplopoma fimbria). Aging of this species has been hampered by poor agreement (averaging less than 45%) among age readers and by differences in assigned ages of as much as 15 years. Otoliths from fish that had been injected with oxytetracycline (OTC) and that had been at liberty for known durations were used to determine why age determinations were so difficult and to help determine the correct aging procedure. All fish were sampled from Oregon southwards, which represents the southern part of their range. The otoliths were examined with the aid of image processing. Some fish showed little or no growth on the otolith after eight months at liberty, whereas otoliths from other fish grew substantially. Some fish lay down two prominent hyaline zones within a single year, one in the summer and one in the winter. We classified the otoliths by morphological type and found that certain types are more likely to lay down multiple hyaline zones and other types are likely to lay down little or no zones. This finding suggests that some improvement could be achieved by detailed knowledge of the growth characteristics of the different types. This study suggests that it may not be possible to obtain reliable ages from sablefish otoliths. At the very least, more studies will be required to under-stand the growth of sablefish otoliths.

The Hudson-Raritan Estuary as a crossroads for distribution of blue (Callinectes sapidus), lady (Ovalipes ocellatus), and Atlantic rock (Cancer irroratus) crabs

Blue (Callinectes sapidus)(Portunidae),lady (Ovalipes ocellatus)(Portunidae), and Atlantic rock (Cancer irroratus) (Cancridae) crabs inhabit estuaries on the northeast United States coast for parts or all of their life cycles. Their distributions overlap or cross during certain seasons. During a 1991–1994 monthly otter trawl survey in the Hudson-Raritan Estuary between New York and New Jersey, blue and lady crabs were collected in warmer months and Atlantic rock crabs in colder months. Sex ratios, male:female, of mature crabs were 1:2.0 for blue crabs, 1:3.1 for lady crabs, and 21.4:1 for Atlantic rock crabs. Crabs, 1286 in total, were subsampled for dietary analysis, and the dominant prey taxa for all crabs, by volume of foregut contents, were mollusks and crustaceans. The proportion of amphipods and shrimp in diets decreased as crab size increased. Trophic niche breadth was widest for blue crabs, narrower for lady crabs, and narrowest for Atlantic rock crabs. Trophic overlap was lowest between lady crabs and Atlantic rock crabs, mainly because of frequent consumption of the dwarf surfclam (Mulinia lateralis) by the former and the blue mussel (Mytilus edulis) by the latter. The result of cluster analysis showed that size class and location of capture of predators in the estuary were more influential on diet than the species or sex of the predators.

Indirect estimates of natural mortality rate for arrowtooth flounder (Atheresthes stomias) and darkblotched rockfish (Sebastes crameri)

Indirect estimates of instantaneous natural mortality rate (M) are widely used in stock assessment and fisheries management. They are essentially a form of meta-analysis, in which prior information on M and key life history parameters from a variety of stocks is used to estimate M for the stock in question.

Modeling red sea urchin (Strongylocentrotus franciscanus) growth using six growth functions

The growth of red sea urchins (Strongylocentrotus franciscanus) was modeled by using tag-recapture data from northern California. Red sea urchins (n=211) ranging in test diameter from 7 to 131 mm were examined for changes in size over one year. We used the function Jt+1 = Jt + f(Jt) to model growth, in which Jt is the jaw size (mm) at tagging, and Jt+1 is the jaw size one year later. The function f(Jt), represents one of six deterministic models: logistic dose response, Gaussian, Tanaka, Ricker, Richards, and von Bertalanffy with 3, 3, 3, 2, 3, and 2 minimization parameters, respectively. We found that three measures of goodness of fi t ranked the models similarly, in the order given. The results from these six models indicate that red sea urchins are slow growing animals (mean of 7.2 ±1.3 years to enter the fishery). We show that poor model selection or data from a limited range of urchin sizes (or both) produces erroneous growth parameter estimates and years-to-fishery estimates. Individual variation in growth dominated spatial variation at shallow and deep sites (F=0.246, n=199, P=0.62). We summarize the six models using a composite growth curve of jaw size, J, as a function of time, t: J = A(B – e–Ct) + Dt, in which each model is distinguished by the constants A, B, C, and D. We suggest that this composite model has the flexibility of the other six models and could be broadly applied. Given the robustness of our results regarding the number of years to enter the fishery, this information could be incorporated into future fishery management plans for red sea urchins in northern California.