Annular Growth Layers In Juvenile Loggerhead Turtles (Caretta-caretta)

Juvenile loggerhead turtles (Caretta caretta) were tagged with tetracycline to establish a chronology for deposition of periosteal bone growth layers. Eight recaptures, encompassing intervals of 1 to 3 years, were used to demonstrate that these growth layers were typically deposited on an annual basis. However, the number of scorable growth layers represents an underestimate of true age because earlier growth layers are obscured by expansion of the medullary cavity during growth. The number of absorbed growth layers was extrapolated from calculations based on juvenile bone growth patterns. Most (83%) of these corrected age estimates for juvenile loggerheads, 40 to 80 cm straight tine carapace length, were between 5 and 15 years

Observations On Distribution And Abundance Of Red Crabs In Norfolk Canyon And Adjacent Continental Slope

The results of June, 1973 trawl and trap sets in the Norfolk Canyon and adjacent slope area are summarized with respect to red crab (Geryon quinquedens) distribution and abundance. Red crabs ranged in depth from 145 to 870 fathoms but were most abundant from 145 to 280 fathoms. This species was more abundant on the adjacent slope area than in Norfolk Canyon. Crabs caught ranged from 2 to 6 inches in carapace width. Most of the crabs were in the hard shell condition but a few peeler, soft, and papershell crabs were also caught, indicating that molting was occurring. The crabs were segregated with regard to sex. Deeper catches had more males, shallower catches had more females. A few ovigerous females were caught in both the canyon and slope area

Demographic Analysis Of The Sandbar Shark, Carcharhinus Plumbeus In The Western North Atlantic

The sandbar shark, Carcharhinus plumbeus, is the most common large coastal shark in Virginia waters and is an important component of recreational and commercial fisheries along the east coast of the United States. Sandbar shark demographic analyses, using known and estimated life history parameters, including fishing mortality (F) at ages and levels estimated in a recent stock assessment, were used to estimate potential population growth and exploitation. Life history tables were constructed by using best estimates of natural mortality (M) of O.11 or 0.07 for maximum ages of 30 or 60 yr, respectively. Natality was fixed at 2.1 female pups/yr. Fishing mortality (F=0.05, 0.10, 0.15, 0.20, or 0.25) was simulated to begin at age 8, 10, 15, 20, or 29. The annual population growth rate was highest under a \u27\u27best-case\u27\u27 scenario of M=0.05 (1/2 best estimate) and maximum age of 30 yr, but was only 11.9%/yr. At M=0.11 for all ages, the population increase rate was 6.4%/yr, and the generation time was about 20 years. At higher juvenile mortality rates, the population growth rate decreased to 2.6%/yr. Adding fishing mortality at immature ages caused the population to decline unless F levels were \u3c 0.10 and 0.05 at maximum age = 30 and 60, respectively. It is apparent that sandbar shark populations will decline under any substantial fishing mortality on immature ages and that mature fish can be exploited only at very low levels

Biology And Distribution Of Species Of Polyacanthonotus (Pisces, Notacanthiformes) In The Western North-Atlantic

The notacanthid genus Poiyacanthonotus is represented in the Atlantic by three species of demersal deep-sea fishes at depths from about 500-3,800 m. Recent collections have made available new material from the temperate and tropical western North Atlantic for life history study of P. merretti and P. rissoanus. Species of the genus are browsers on small benthic macrofauna including polychaetes, gammaridean amphipods, and mysids. Reproduction does not appear to be seasonal. Fecundity is positively correlated with size in P. merretti, and ranges between 1,900-5,700 ova. Fecundities are much higher (ca. 20,000-30,000 ova) in P. rissoanus and P. cha/lengeri, which attain a larger size. Sex ratios appear highly skewed. Among western Atlantic material, males were found only in P. merretti, with a female: male sex ratio of 25: l. No bigger-deeper relationship was found in P. merretti or P. rissoanus. Despite overlapping geographic and bathymetric ranges, species of Poiyacanthonotus tend to be allopatric in distribution. The amphi-Atlantic P. merretti is predominantly tropical at bathyal depths (584-2,000 m). The circumglobal species P. cha/lengeri is predominantly antitropical on the continental rise (1,302-3,753 m, mostly below 2,000 m). The Atlantic species P. rissoanus is also predominantly anti-tropical on the continental slope (500-2,875 m, mostly above 2,000 m)

Bottom-up and climatic forcing on the worldwide population of leatherback turtles

Nesting populations of leatherback turtles (Dermochelys coriacea) in the Atlantic and western Indian Oceans are increasing or stable while those in the Pacific are declining. It has been suggested that leatherbacks in the eastern Pacific may be resource limited due to environmental variability derived from the El Nino Southern Oscillation (ENSO), but this has yet to be tested. Here we explored bottom-up forcing and the responding reproductive output of nesting leatherbacks worldwide. We achieved this through an extensive review of leatherback nesting and migration data and by analyzing the spatial, temporal, and quantitative nature of resources as indicated by net primary production at post-nesting female migration and foraging areas. Leatherbacks in the eastern Pacific were the smallest in body size and had the lowest reproductive output due to less productive and inconsistent resources within their migration and foraging areas. This derived from natural interannual and multidecadal climate variability together with an influence of anthropogenic climate warming that is possibly affecting these natural cycles. The reproductive output of leatherbacks in the Atlantic and western Indian Oceans was nearly twice that of turtles in the eastern Pacific. The inconsistent nature of the Pacific Ocean may also render western Pacific leatherbacks susceptible to a more variable reproductive output; however, it appears that egg harvesting on nesting beaches is their major threat. We suggest that the eastern Pacific leatherback population is more sensitive to anthropogenic mortality due to recruitment rates that are lower and more variable, thus accounting for much of the population differences compared to Atlantic and western Indian turtles

Comparative visual function in four piscivorous fishes inhabiting Chesapeake Bay

Maintaining optimal visual performance is a difficult task in photodynamic coastal and estuarine waters because of the unavoidable tradeoffs between luminous sensitivity and spatial and temporal resolution, yet the visual systems of coastal piscivores remain understudied despite differences in their ecomorphology and microhabitat use. We therefore used electroretinographic techniques to describe the light sensitivities, temporal properties and spectral sensitivities of the visual systems of four piscivorous fishes common to coastal and estuarine waters of the western North Atlantic: striped bass (Morone saxatilis), bluefish (Pomatomus saltatrix), summer flounder (Paralichthys dentatus) and cobia (Rachycentron canadum). Benthic summer flounder exhibited higher luminous sensitivity and broader dynamic range than the three pelagic foragers. The former were at the more sensitive end of an emerging continuum for coastal fishes. By contrast, pelagic species were comparatively less sensitive, but showed larger day-night differences, consistent with their use of diel light-variant photic habitats. Flicker fusion frequency experiments revealed significant interspecific differences at maximum intensities that correlated with lifestyle and habitat. Spectral responses of most species spanned 400-610nm, with significant day-night differences in striped bass and bluefish. Anadromous striped bass additionally responded to longer wavelengths, similar to many freshwater fishes. Collectively, these results suggest that pelagic piscivores are well adapted to bright photoclimates, which may be at odds with the modern state of eutrified coastal and estuarine waters that they utilize. Recent anthropogenic degradation of water quality in coastal environments, at a pace faster than the evolution of visual systems, may impede visually foraging piscivores, change selected prey, and eventually restructure ecosystems

Comparative visual function in five sciaenid fishes inhabiting Chesapeake Bay

Maintaining optimal visual performance is a difficult task in the photodynamic coastal and estuarine waters in which western North Atlantic sciaenid fishes support substantial commercial and recreational fisheries. Unavoidable tradeoffs exist between visual sensitivity and resolution, yet sciaenid visual systems have not been characterized despite strong species-specific ecomorphological and microhabitat differentiation. We therefore used electroretinographic techniques to describe the light sensitivities, temporal properties, and spectral characteristics of the visual systems of five sciaenids common to Chesapeake Bay, USA: weakfish (Cynoscion regalis), spotted seatrout (Cynoscion nebulosus), red drum (Sciaenops ocellatus), Atlantic croaker (Micropogonias undulatus) and spot (Leiostomus xanthurus). Benthic sciaenids exhibited higher sensitivities and broader dynamic ranges in white light V/logI experiments than more pelagic forms. Sensitivities of the former were at the lower (more sensitive) end of an emerging continuum for coastal fishes. Flicker fusion frequency experiments revealed significant interspecific differences at maximum intensities that correlated with lifestyle and habitat, but no specific differences at dimmer intensities. Spectral responses of most sciaenids spanned 400-610 nm, with significant diel differences in weakfish and Atlantic croaker. Weakfish, a crepuscular predator, also responded to ultraviolet wavelengths; this characteristic may be more useful under less turbid conditions. Collectively, these results suggest that sciaenids are well adapted to the dynamic photoclimate of the coastal and estuarine waters they inhabit. However, the recent anthropogenic degradation of water quality in coastal environments, at a pace faster than the evolution of visual systems, has amplified the importance of characterizing visual function in managed aquatic fauna

Acoustic pressure and particle motion thresholds in six sciaenid fishes

Sciaenid fishes are important models of fish sound production, but investigations into their auditory abilities are limited to acoustic pressure measurements on five species. In this study, we used auditory brainstem response ( ABR) to assess the pressure and particle acceleration thresholds of six sciaenid fishes commonly found in Chesapeake Bay, eastern USA: weakfish ( Cynoscion regalis), spotted seatrout ( Cynoscion nebulosus), Atlantic croaker ( Micropogonias undulatus), red drum ( Sciaenops ocellatus), spot ( Leiostomus xanthurus) and northern kingfish ( Menticirrhus saxatilis). Experimental subjects were presented with pure 10 ms tone bursts in 100 Hz steps from 100 Hz to 1.2 kHz using an airborne speaker. Sound stimuli, monitored with a hydrophone and geophone, contained both pressure and particle motion components. Sound pressure and particle acceleration thresholds varied significantly among species and between frequencies; audiograms were notably flatter for acceleration than pressure at low frequencies. Thresholds of species with diverticulae projecting anteriorly from their swim bladders ( weakfish, spotted seatrout, and Atlantic croaker) were typically but not significantly lower than those of species lacking such projections ( red drum, spot, northern kingfish). Sciaenids were most sensitive at low frequencies that overlap the peak frequencies of their vocalizations. Auditory thresholds of these species were used to estimate idealized propagation distances of sciaenid vocalizations in coastal and estuarine environments

Age and growth of the smooth hammerhead, Sphyrna zygaena, in the Atlantic Ocean: comparison with other hammerhead species

The smooth hammerhead Sphyrna zygaena (Sphyrnidae) is a pelagic shark occasionally caught as bycatch in pelagic longline fisheries, but is one of the least studied of all pelagic sharks. Age and growth of S. zygaena was studied along a wide Atlantic region covering both the northern and southern hemispheres. Data from 304 specimens, caught between October 2009 and September 2014, ranging in size from 126 to 253 cm fork length (FL), were analysed. Growth models were fitted using the three-parameter von Bertalanffy growth function (VBGF) re-parameterized to calculate L0 (size at birth). Growth models were fitted to the sample data and data from several back-calculation models. The model fit to the quadratic modified Dahl-Lea back-calculated data seems to be the most appropriate to describe growth in this species, with resulting growth parameters of Linf = 285 cm FL, k = 0.09 year−1 for males and Linf = 293 cm FL, k = 0.09 year−1 for females. Compared with other species of the same genus, estimated growth coefficients for S. zygaena seem to fall in the low to middle range. Although further work is still needed, this study adds to knowledge of the vital life-history parameters of smooth hammerheads in the Atlantic Ocean, which can be used in the management and conservation of this species.Programa Operacional Potencial Humano: IF/00253/2014info:eu-repo/semantics/publishedVersio

Migrations and habitat use of the smooth hammerhead shark (Sphyrna zygaena) in the Atlantic Ocean

The smooth hammerhead shark, Sphyrna zygaena, is a cosmopolitan semipelagic shark captured as bycatch in pelagic oceanic fisheries, especially pelagic longlines targeting swordfish and/or tunas. From 2012 to 2016, eight smooth hammerheads were tagged with Pop-up Satellite Archival Tags in the inter-tropical region of the Northeast Atlantic Ocean, with successful transmissions received from seven tags (total of 319 tracking days). Results confirmed the smooth hammerhead is a highly mobile species, as the longest migration ever documented for this species (> 6600 km) was recorded. An absence of a diel vertical movement behavior was noted, with the sharks spending most of their time at surface waters (0-50 m) above 23 degrees C. The operating depth of the pelagic long-line gear was measured with Minilog Temperature and Depth Recorders, and the overlap with the species vertical distribution was calculated. The overlap is taking place mainly during the night and is higher for juveniles (similar to 40% of overlap time). The novel information presented can now be used to contribute to the provision of sustainable management tools and serve as input for Ecological Risk Assessments for smooth hammerheads caught in Atlantic pelagic longline fisheries.Oceanario de Lisboa through Project "SHARK-TAG: Migrations and habitat use of the smooth hammerhead shark in the Atlantic Ocean"; Investigador-FCT from the Portuguese Foundation for Science and Technology (FCT, Fundacao para a Ciencia e Tecnologia) [Ref: IF/00253/2014]; EU European Social Fund; Programa Operacional Potencial Human