10 resultados para 13077-024

em Aquatic Commons


Relevância:

10.00% 10.00%

Publicador:

Resumo:

To be in compliance with the Endangered Species Act and the Marine Mammal Protection Act, the United States Department of the Navy is required to assess the potential environmental impacts of conducting at-sea training operations on sea turtles and marine mammals. Limited recent and area-specific density data of sea turtles and dolphins exist for many of the Navy’s operations areas (OPAREAs), including the Marine Corps Air Station (MCAS) Cherry Point OPAREA, which encompasses portions of Core and Pamlico Sounds, North Carolina. Aerial surveys were conducted to document the seasonal distribution and estimated density of sea turtles and dolphins within Core Sound and portions of Pamlico Sound, and coastal waters extending one mile offshore. Sea Surface Temperature (SST) data for each survey were extracted from 1.4 km/pixel resolution Advanced Very High Resolution Radiometer remote images. A total of 92 turtles and 1,625 dolphins were sighted during 41 aerial surveys, conducted from July 2004 to April 2006. In the spring (March – May; 7.9°C to 21.7°C mean SST), the majority of turtles sighted were along the coast, mainly from the northern Core Banks northward to Cape Hatteras. By the summer (June – Aug.; 25.2°C to 30.8°C mean SST), turtles were fairly evenly dispersed along the entire survey range of the coast and Pamlico Sound, with only a few sightings in Core Sound. In the autumn (Sept. – Nov.; 9.6°C to 29.6°C mean SST), the majority of turtles sighted were along the coast and in eastern Pamlico Sound; however, fewer turtles were observed along the coast than in the summer. No turtles were seen during the winter surveys (Dec. – Feb.; 7.6°C to 11.2°C mean SST). The estimated mean surface density of turtles was highest along the coast in the summer of 2005 (0.615 turtles/km², SE = 0.220). In Core and Pamlico Sounds the highest mean surface density occurred during the autumn of 2005 (0.016 turtles/km², SE = 0.009). The mean seasonal abundance estimates were always highest in the coastal region, except in the winter when turtles were not sighted in either region. For Pamlico Sound, surface densities were always greater in the eastern than western section. The range of mean temperatures at which turtles were sighted was 9.68°C to 30.82°C. The majority of turtles sighted were within water ≥ 11°C. Dolphins were observed within estuarine waters and along the coast year-round; however, there were some general seasonal movements. In particular, during the summer sightings decreased along the coast and dolphins were distributed throughout Core and Pamlico Sounds, while in the winter the majority of dolphins were located along the coast and in southeastern Pamlico Sound. Although relative numbers changed seasonally between these areas, the estimated mean surface density of dolphins was highest along the coast in the spring of 2006 (9.564 dolphins/km², SE = 5.571). In Core and Pamlico Sounds the highest mean surface density occurred during the autumn of 2004 (0.192 dolphins/km², SE = 0.066). The estimated mean surface density of dolphins was lowest along the coast in the summer of 2004 (0.461 dolphins/km², SE = 0.294). The estimated mean surface density of dolphins was lowest in Core and Pamlico Sounds in the summer of 2005 (0.024 dolphins/km², SE = 0.011). In Pamlico Sound, estimated surface densities were greater in the eastern section except in the autumn. Dolphins were sighted throughout the entire range of mean SST (7.60°C to 30.82°C), with a tendency towards fewer dolphins sighted as water temperatures increased. Based on the findings of this study, sea turtles are most likely to be encountered within the OPAREAs when SST is ≥ 11°C. Since sea turtle distributions are generally limited by water temperature, knowing the SST of a given area is a useful predictor of sea turtle presence. Since dolphins were observed within estuarine waters year-round and throughout the entire range of mean SST’s, they likely could be encountered in the OPAREAs any time of the year. Although our findings indicated the greatest number of dolphins to be present in the winter and the least in the summer, their movements also may be related to other factors such as the availability of prey. (PDF contains 28 pages)

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The introduction of a long-term management plan for the cod socks by the International Baltic Sea Fishery Commission (IBSFC) to ensure stable and high yields and to conserve the fish stocks of the Baltic demands certain conservation measures. One is the use of the Total Allowable Catches (TACs) based on precautionary approches. In addition the exploitation pattern and the selectivy of trawls shall be improved to increase the spawning stock biomass and to reduce the presently high discard rates. The contributation demonstrates by means of model calculations for the cod stock of the ICES Sub-divisions 22 to 24 ( Western Baltic ) the short- and long-term effects of an improvement of the trawl selectivity on stock size, yields and profit.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The level and distribution of some heavy metals viz Cadmium, Lead, Copper Zinc, and Cobalt in five commercially important fishes, water and sediments at three different locations in Kainj Lake were determined using standard methods. The results show that the ranges of heavy metals mu g/g in fishes in Dam site Laotian are: Cd (0.05~c0.01-20~c01), (Pb(ND-1.12 plus or minus )1), Cu (0.81~c25-2.93~c06), Zn (20.89 arrow right .15-36.78~c2.97), Co(0.08~c01-0.27~c02); in cover Dam, the ranges are Cd (0.04~c02-0.16~c0.2), Pb (nd-02~c01), Cu(0.75~c05-2.61~c13), Zn(15.70~c1.55-32.23~c2.70), Co(0.04~c02-0.25~c0.01) and in Yuna they are Cd (0.05~c01-0.14~c02), Pb (nd-0.32~c01), Cu (0.23~c07-2.70~c05), Zn(15.50 plus or minus `.35-25.62~c2.47), Co(0.07~c02-23~c0.01). The metals concentration (mg/l) in the water sample from Dam site, cover dam and Yuna respectively are Cd(0.007~c001,. 004~c001 and 0.005~001), Pb(013~c001, ND and ND), Cu(.055~c008.030~c007, 05 plus or minus .010), Zn(0.13~c01, 0.060 plus or minus .0055) and Co (.026 plus or minus .022 plus or minus .004, .024 plus or minus .004), while the metals concentration ( mu g/g) in sediments sample from Dam site, cover dam and Yuna are respectively Cd(.05 plus or minus .01, .02 plus or minus .01), Pb(16.00~c1.00, ND and 9.33~c1.01), Cu(24.00~c1.34, 4.26 plus or minus .91 and 11.08~c1.32), Zn(42.00~c1.00, 35~c10 and 38.00 plus or minus .45), Co(15.00~c1.17, 8.69~c1.21 and 10.91~c44). The concentrations of the tested heavy metals are within the acceptable standards of WHO (1987a)

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Proportions of American alligator (Alligator mississippiensis) nests sighted during aerial survey in Florida were estimated based upon multiple surveys by different observers. We compared sighting proportions across habitats, nesting seasons, and observer experience levels. The mean sighting proportion across all habitats and years was 0.736 (SE=0.024). Survey counts corrected by the mean sighting proportion reliably predicted total nest counts (R2=0.933). Sighting proportions did not differ by habitat type (P=0.668) or year P=0.328). Experienced observers detected a greater proportion of nests (P

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Parameters of the exponential body length (L)-fecundity (F) relationship of the form F=a.L super(b) are presented for 47 populations and 26 species of Nigerian fishes. Estimates of b varied between 1.563 (Ilisha africana) and 5.771 (Barbus callipterus) with a mean of 3.054 (s.d. = 1.024). The maximum sizes of fish populations examined did not significantly influence the relative magnitudes of b. The parameters Alpha and Beta of the linear length-fecundity relationships of the form F = Alpha + BetaL are also presented for five fish populations. Estimates of Beta ranged from 243.5 (Chrysichthys walkeri) to 1,334,895 (Tilapia mariae).

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The foraging ecology of bottlenose dolphins Tursiops truncatus in the Northwest Florida Panhandle and estuaries in northern Georgia was determined using diet analysis and behavioral surveys. Stomach content analysis was completed on bottlenose dolphins(N = 25) that stranded in the Northwest Florida Panhandle from November 2006 to March 2009. The most abundant prey species were spot Leiostomus xanthurus (20.4%), squid (10.9%), pinfish Lagodon rhombiodes (10.3%), and Atlantic croaker Micropogonias undulatus (8.5%). Dolphins that stranded during months with a red tide Karenia brevis bloom consumed more pinfish, and spot; whereas dolphins that stranded in non-bloom months consumed more squid, Atlantic croaker, and silver perch Bairdiella chrysoura. Differences in diet were also identified for dolphins that stranded inside bays/sound and dolphin that stranded outside of bays along the coast, and male and female dolphins. Surveys were conducted from south of the Savannah River to north of Ossabaw Sound in Georgia where foraging behaviors were classified. Multivariate Generalized Additive Models were used to test correlations of behaviors to dolphin group size, depth, salinity, temperature, creek width, and tide. Sightings with headstands (p = 0.009), hard stops (p = 0.019), chasing (p = 0.004), mudbank whacking (p < 0.001), herding/circling (p = 0.024), and strand feeding (p = 0.006) were correlated with shallow water or small creeks. Sightings with kerplunking (p = 0.031), mudbank whacking (p = 0.001), strand feeding (p = 0.003), and herding/circling (p = 0.026) were significantly correlated with low tide. The results of the Savannah, Georgia study were the first to characterize foraging behaviors in this area and demonstrate how bottlenose dolphins utilize the salt marsh estuary in terms of foraging. Studies like these are important to determine how dolphins forage efficiently and to provide background information on diet and foraging behavior for use in monitoring future impacts to dolphins in the Northwest Florida Panhandle and near Savannah, Georgia.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The life history of the Atlantic sharpnose shark (Rhizoprionodon terraenovae) was described from 1093 specimens collected from Virginia to northern Florida between April 1997 and March 1999. Longitudinally sectioned vertebral centra were used to age each specimen, and the periodicity of circuli deposition was verified through marginal increment analysis and focus-to-increment frequency distributions. Rhizoprionodon terraenovae reached a maximum size of 828 mm precaudal length (PCL) and a maximum age of 11+ years. Mean back-calculated lengths-at-age ranged from 445 mm PCL at age one to 785 mm PCL at age ten for females, and 448 mm PCL at age one to 747 mm PCL at age nine for males. Observed lengthat-age data (estimated to 0.1 year) yielded the following von Bertalanffy parameters estimates: L∞= 749 mm PCL (SE=4.60), K = 0.49 (SE=0.020), and t0= –0.94 (SE=0.046) for females; and L∞= 745 mm PCL (SE = 5.93), K = 0.50 (SE=0.024), and t0= –0.91 (SE = 0.052) for males. Sexual maturity was reached at age three and 611 mm PCL for females, and age three and 615 mm PCL for males. Rhizoprionodon terraenovae reproduced annually and had a gestation period of approximately 11 months. Litter size ranged from one to eight (mean=3.85) embyros, and increased with female PCL.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Effects of post-ovulatory and post-stripping retention time and temperature on egg viability rates were studied in kutum (Rutilus frisii kutum). Eggs were retained inside (in vivo storage) or outside the ovarian cavity with ovarian fluid (in vitro storage) at various temperatures. Two experiments were performed: 1) Partial volumes of eggs were stripped and fertilized at 24- hour intervals for 96 hours post-ovulation (HPO) (at 11 °C) and at 12-hour intervals for 72 HPO (at 14 °C), and 2) stored eggs were fertilized after 0, 2, 4, 6, and 8 hours post-stripping (HPS) at temperatures of 4, 10, 12, and 26 °C. In the first experiment, the highest eyeing and hatching rates (76% and 60% at 11 °C; 81% and 71% at 14 °C) and the lowest eyed-egg mortalities (20% at 11 °C; 12% at 14 °C) occurred in the eggs fertilized immediately (0–24 HPO at 11 °C and 0–12 HPO at 14 °C) after ovulation. Egg viability, as shown by successful eyeing and hatching rates, was completely lost by 72–96 HPO at 11 °C, and 60–72 HPO at 14 °C. In the second experiment, the maximum eyeing (87%) and hatching (75%) rates of eggs took place at 0 HPS followed by 8 HPS (> 80% and > 70%, respectively) at 4 °C. As storage temperature increased, egg viability decreased: 80%, 70%, and 50% viable at 8 HPS at 4, 10, and 12 °C, respectively. The eggs stored at 26 °C lost their viability almost completely after 4 HPS. Eyed-egg mortality increased from 13% at 0 HPS to 48.2% at 4 HPS at 26°C. These results demonstrate that egg stripping should take place within 168 °C-hours after ovulation and that complete loss of viability of the eggs occurs by 672°C-hours after ovulation. The in vivo storage method is more effective compared to in vitro storage. Also successful in vitro storage of eggs can be used atleast within 8 hours at temperatures ranging from 4 to 12ºC.