Using productivity and susceptibility indices to assess the vulnerability of United States fish stocks to overfishing

Assessing the vulnerability of stocks to fishing practices in U.S. federal waters was recently highlighted by the National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration, as an important factor to consider when 1) identifying stocks that should be managed and protected under a fishery management plan; 2) grouping data-poor stocks into relevant management complexes; and 3) developing precautionary harvest control rules. To assist the regional fishery management councils in determining vulnerability, NMFS elected to use a modified version of a productivity and susceptibility analysis (PSA) because it can be based on qualitative data, has a history of use in other fisheries, and is recommended by several organizations as a reasonable approach for evaluating risk. A number of productivity and susceptibility attributes for a stock are used in a PSA and from these attributes, index scores and measures of uncertainty are computed and graphically displayed. To demonstrate the utility of the resulting vulnerability evaluation, we evaluated six U.S. fisheries targeting 162 stocks that exhibited varying degrees of productivity and susceptibility, and for which data quality varied. Overall, the PSA was capable of differentiating the vulnerability of stocks along the gradient of susceptibility and productivity indices, although fixed thresholds separating low-, moderate-, and highly vulnerable species were not observed. The PSA can be used as a flexible tool that can incorporate regional-specific information on fishery and management activity.

Flatfish herding behavior in response to trawl sweeps: a comparison of diel responses to conventional sweeps and elevated sweeps

Commercial bottom trawls often have sweeps to herd fish into the net. Elevation of the sweeps off the seaf loor may reduce seafloor disturbance, but also reduce herding effectiveness. In both field and laboratory experiments, we examined the behavior of flatfish in response to sweeps. We tested the hypotheses that 1) sweeps are more effective at herding flatfish during the day than at night, when fish are unable to see approaching gear, and that 2) elevation of sweeps off the seafloor reduces herding during the day, but not at night. In sea trials, day catches were greater than night catches for four out of six flatfish species examined. The elevation of sweeps 10 cm significantly decreased catches during the day, but not at night. Laboratory experiments revealed northern rock sole (Lepidopsetta polyxystra) and Pacific halibut (Hippoglossus stenolepis) were more likely to be herded by the sweep in the light, whereas in the dark they tended to pass under or over the sweep. In the light, elevation of the sweep reduced herding, and more fish passed under the sweep. In contrast, in the dark, sweep elevation had little effect upon the number of fish that exhibited herding behavior. The results of both field and laboratory experiments were consistent with the premise that vision is the principle sensory input that controls fish behavior and orientation to trawl gear, and gear performance will differ between conditions where flatfish can see, in contrast to where they cannot see, the approaching gear.

Measurement errors in body size of sea scallops (Placopecten magellanicus) and their effect on stock assessment models

Body-size measurement errors are usually ignored in stock assessments, but may be important when body-size data (e.g., from visual sur veys) are imprecise. We used experiments and models to quantify measurement errors and their effects on assessment models for sea scallops (Placopecten magellanicus). Errors in size data obscured modes from strong year classes and increased frequency and size of the largest and smallest sizes, potentially biasing growth, mortality, and biomass estimates. Modeling techniques for errors in age data proved useful for errors in size data. In terms of a goodness of model fit to the assessment data, it was more important to accommodate variance than bias. Models that accommodated size errors fitted size data substantially better. We recommend experimental quantification of errors along with a modeling approach that accommodates measurement errors because a direct algebraic approach was not robust and because error parameters were diff icult to estimate in our assessment model. The importance of measurement errors depends on many factors and should be evaluated on a case by case basis.

Feeding ecology of Atlantic bluefin tuna (Thunnus thynnus) in North Carolina: diet, daily ration, and consumption of Atlantic menhaden (Brevoortia tyrannus)

Diet, gastric evacuation rates, daily ration, and population-level prey demand of bluefin tuna (Thunnus thynnus) were estimated in the continental shelf waters off North Carolina. Bluefin tuna stomachs were collected from commercial fishermen during the late fall and winter months of 2003–04, 2004–05, and 2005–06. Diel patterns in mean gut fullness values were used to estimate gastric evacuation rates. Daily ration determined from mean gut fullness values and gastric evacuation rates was used, along with bluefin tuna population size and residency times, to estimate population-level consumption by bluefin tuna on Atlantic menhaden (Brevoortia tyrannus). Bluefin tuna diet (n= 448) was dominated by Atlantic menhaden; other teleosts, portunid crabs, and squid were of mostly minor importance. The time required to empty the stomach after peak gut fullness was estimated to be ~20 hours. Daily ration estimates were approximately 2% of body weight per day. At current western Atlantic population levels, bluefin tuna predation on Atlantic menhaden is minimal compared to predation by other known predators and the numbers taken in commercial harvest. Bluefin tuna appear to occupy coastal waters in North Carolina during winter to prey upon Atlantic menhaden. Thus, changes in the Atlantic menhaden stock status or distribution would alter the winter foraging locations of bluefin

Prevalence of the commensal barnacle Xenobalanus globicipitis on cetacean species in the eastern tropical Pacific Ocean, and a review of global occurrence

Distribution and prevalence of the phoretic barnacle Xenobalanus on cetacean species are reported for 22 cetaceans in the eastern tropical Pacific Ocean (21 million km2). Four cetacean species are newly reported hosts for Xenobalanus: Bryde’s whale (Balaenoptera edeni), long-beaked common dolphin (Delphinus capensis), humpback whale (Megaptera novaeangliae), and spinner dolphin (Stenella longirostris). Sightings of Xenobalanus in pelagic waters are reported for the first time, and concentrations were located within three productive zones: near the Baja California peninsula, the Costa Rica Dome and waters extending west along the 10°N Thermocline Ridge, and near Peru and the Galapagos Archipelago. Greatest prevalence was observed on blue whales (Balaenoptera musculus) indicating that slow swim speeds are not necessary for effective barnacle settlement. Overall, prevalence and prevalence per sighting were generally lower than previously reported. The number of barnacles present on an individual whale was greatest for killer whales, indicating that Xenobalanus larvae may be patchily distributed. The broad geographic distribution and large number of cetacean hosts, indicate an extremely cosmopolitan distribution. A better understanding of the biology of Xenobalanus is needed before this species can be used as a biological tag.

Paul Ricoeur e a consciência como tarefa: o percurso da reflexão

Este trabalho busca principalmente reconhecer o que considera ser a dimensão sistemática do pensamento de Paul Ricoeur, fundada, como se acredita, na concepção da consciência como tarefa. Procura outrossim compreender os pressupostos ontológicos e metodológicos de seu pensamento. Pretende mostrar também que, ao perseguir uma simbólica dos sentidos múltiplos, a reflexão concreta de Ricoeur integra, a partir do que ele chama dom da linguagem, o logos filosófico, a episteme que virou ciência e a riqueza pré-filosófica do símbolo. Sua hermenêutica filosófica busca a compreensão do si, da reflexão sobre si mesmo, através da interpretação aplicada sobre os signos e símbolos de uma consciência que não se sabe no princípio, mas ao cabo do desvio de suas obras e de seus atos. A reflexão é a reapropriação daquilo que se é a partir do que é dito a si mesmo pelos signos e símbolos da cultura e das tradições. Paul Ricoeur é apresentado ainda como crítico da consciência imediata e narcísica. Ele constrói seu percurso intelectual de sorte a arbitrar o conflito das diversas interpretações que versam sobre o simbolismo humano. Este trabalho procura mostrar finalmente que o filósofo propõe de fato um novo percurso para a reflexão, através de uma démarche em dois tempos, em que o pensamento reflexivo se desapossa do imediatismo da consciência falsa e comum, para posteriormente se reapropriar das significações mais profundas manifestadas em nosso esforço para existir e nutridas pelo nosso desejo de ser. Eis a trajetória hist��rica e exemplar que esta dissertação busca evidenciar.

Variability in spawning frequency and reproductive development of the narrow-barred Spanish mackerel (Scomberomorus commerson) along the west coast of Australia

The narrow-barred Spanish mackerel (Scomberomorus commerson) is widespread throughout the Indo-West Pacific region. This study describes the reproductive biology of S. commerson along the west coast of Australia, where it is targeted for food consumption and sports fishing. Development of testes occurred at a smaller body size than for ovaries, and more than 90% of males were sexually mature by the minimum legal length of 900 mm TL compared to 50% of females. Females dominated overall catches although sex ratios within daily catches vary considerably and females were rarely caught when spaw n ing. Scomberomorus commerson are seasonally abundant in coastal waters and most of the commercial catch is taken prior to the reproductive season. Spawning occurs between about August and November in the Kimberley region and between October and January in the Pilbara region. No spawning activity was recorded in the more southerly West Coast region, and only in the north Kimberley region were large numbers of fish with spawning gonads collected. Catches dropped to a minimum when spawning began in the Pilbara region, when fish became less abundant in inshore waters and inclement weather conditions limited fishing on still productive offshore reefs. Final maturation and ovulation of oocytes took place within a 24-hour period, and females spawned in the afternoon-evening every three days. A third of these spawning females released batches of eggs on consecutive days. Relationships between length, weight, and batch fecundity are presented.

Age and growth estimates of the thorny skate (Amblyraja radiata) in the western Gulf of Maine

The northwest Atlantic population of thorny skates (Amblyraja radiata) inhabits an area that ranges from Greenland and Hudson Bay, Canada, to South Carolina. Despite such a wide range, very little is known about most aspects of the biology of this species. Recent stock assessment studies in the northeast United States indicate that the biomass of the thorny skate is below the threshold levels mandated by the Sustainable Fisheries Act. In order to gain insight into the life history of this skate, we estimated age and growth for thorny skates, using vertebral band counts from 224 individuals ranging in size from 29 to 105 cm total length (TL). Age bias plots and the coefficient of variation indicated that our aging method represents a nonbiased and precise approach for the age assessment of A. radiata. Marginal increments were significantly different between months (Kruskal-Wallis P<0.001); a distinct trend of increasing monthly increment growth began in August. Age-at-length data were used to determine the von Bertalanffy growth parameters for this population: L∞ = 127 cm (TL) and k= 0.11 for males; L∞ = 120 cm (TL) and k= 0.13 for females. The oldest age estimates obtained for the thorny skate were 16 years for both males and females, which corresponded to total lengths of 103 cm and 105 cm, respectively.

Skimmers: Their Development and Use in Coastal Louisiana

The origin, development, and utilization of the skimmer net is reviewed along with other historical shrimp gears used in coastal Louisiana. The skimmer was developed to catch white shrimp, Penaeus setiferus, observed jumping over the cork line (headrope) of trawls being worked in shallow waters. A description of the gear is presented including basic components and various frame designs used by fishermen during its development. The advantages of skimmers over bottom trawls include: multiple use as both trawl and butterfly net (wing net), ease of deployment, increased maneuverability, reduction and greater survivability of bycatch, and ability to cover more area due to increased speed and continuous fishing capability. Disadvantages may include compromising vessel stability when stored upright on the deck, possible damage to water bottoms when improperly rigged, and limitation to a 12-foot (3.6 m) maximum depth due to size restrictions. The growing popularity of the skimmer net is evident by its introduction into North Carolina and inquiries from other southeastern Atlantic and Gulf coast states.

New Products and Markets for Menhaden, Brevoortia spp.

Although menhaden, Brevoortia spp., represent 23.5 percent of United States commercial fishery landings, they represent only about 2.6 percent of the total landed value of fishery products. New food products and markets are needed to increase the economic value of the menhaden resource. This paper describes investigations of menhaden as a raw material for both traditional and new forms of food products. Canned menhaden is a logical food product, but the production of a menhaden surimi with good functionality has recently been demonstrated. The U.S. Food and Drug Administration has placed partially hydrogenated menhaden oil on the GRAS list of ingredients for food products, but a decision on the status of nutritionally beneficial refined menhaden oil is not yet available. Refined menhaden oil is currently the raw material for biomedical test materials being used in research approved by the National Institutes of Health to determine the health benefits of fish oils and omega-3 fatty acids. The test materials are being produced, with strict quality controls, at the NMFS Charleston Laboratory.

Atlantic-Mediterranean and within-Mediterranean molecular variation in Coris julis (L. 1758) (Teleostei, Labridae)

Sequence variation in the mitochondrial control region was studied in the Mediterranean rainbow wrasse (Coris julis), a species with pronounced pelagic larval phase inhabiting the Mediterranean Sea and the adjacent coastal eastern Atlantic Ocean. A total of 309 specimens from 19 sampling sites were analysed with the aim of elucidating patterns of molecular variation between the Atlantic and the Mediterranean as well as within the Mediterranean Sea. Phylogeographic analyses revealed a pronounced structuring into a Mediterranean and an Atlantic group. Samples from a site at the Moroccan Mediterranean coast in the Alboran Sea showed intermediate frequencies of “Mediterranean” and “Atlantic” haplotypes. We recognised a departure from molecular neutrality and a star-like genealogy for samples from the Mediterranean Sea, which we propose to have happened due to a recent demographic expansion. The results are discussed in the light of previous studies on molecular variation in fish species between the Atlantic and the Mediterranean and within the Mediterranean.

Seasonal and interannual variation in juvenile salmonids and associated fish assemblage in open waters of the lower Columbia River estuary

The transition between freshwater and marine environments is associated with high mortality for juvenile anadromous salmonids, yet little is known about this critical period in many large rivers. To address this deficiency, we investigated the estuarine ecology of juvenile salmonids and their associated fish assemblage in open-water habitats of the lower Columbia River estuary during spring of 2007–10. For coho (Oncorhynchus kisutch), sockeye (O. nerka), chum (O. keta), and yearling (age 1.0) Chinook (O. tshawytscha) salmon, and steelhead (O. mykiss), we observed a consistent seasonal pattern characterized by extremely low abundances in mid-April, maximum abundances in May, and near absence by late June. Subyearling (age 0.0) Chinook salmon were most abundant in late June. Although we observed interannual variation in the presence, abundance, and size of juvenile salmonids, no single year was exceptional across all species-and-age classes. We estimated that >90% of juvenile Chinook and coho salmon and steelhead were of hatchery origin, a rate higher than previously reported. In contrast to juvenile salmonids, the abundance and composition of the greater estuarine fish assemblage, of which juvenile salmon were minor members, were extremely variable and likely responding to dynamic physical conditions in the estuary. Comparisons with studies conducted 3 decades earlier suggest striking changes in the estuarine fish assemblage—changes that have unknown but potentially important consequences for juvenile salmon in the Columbia River estuary.

Effects of land use and physicochemical water quality on grass shrimp, Palaemonetes pugio, and its parasitic isopod, Probopyrus pandalicola, in South Carolina, USA tidal creeks

Grass shrimp, Palaemonetes pugio, are a common inhabitant of US East and Gulf coast salt marshes and are a food source for recreationally and economically important fish and crustacean species. Due to the relationship of grass shrimp with their ecosystem, any significant changes in grass shrimp population may have the potential to affect the estuarine system. Land use is a crucial concern in coastal areas where increasing development impacts the surrounding estuaries and salt marshes and has made grass shrimp population studies a logical choice to investigate urbanization effects. Any impact on tidal creeks will be an impact on grass shrimp populations and their associated micro-environment whether predator, prey or parasitic symbiont. Anthropogenic stressors introduced into the grass shrimp ecosystem may even change the intensity of infections from parasitic symbionts. An ectoparasite found on P. pugio is the bopyrid isopod Probopyrus pandalicola. Little is known about factors that may affect the occurrence of this isopod in grass shrimp populations. The goal was to analyze the prevalence of P. pandalicola in grass shrimp in relation to land use classifications, water quality parameters, and grass shrimp population metrics. Eight tidal creeks in coastal South Carolina were sampled monthly over a three year period. The occurrence of P. pandalicola ranged from 1.2% to 5.7%. Analysis indicated that greater percent water and marsh coverage resulted in a higher incidence of bopyrid occurrence. Analysis also indicated that higher bopyrid incidence occurred in creeks with higher salinity, temperature, and pH but lower dissolved oxygen. The land use characteristics found to limit bopyrid incidence were limiting to grass shrimp (definitive host) populations and probably copepod (intermediate host) populations as well.