Absorption of food in the black-jaw tilapia, Sarotherodon melanotheron (Ruppell) from a small tropical man-made lake in Ibadan, Nigeria

The carbohydrate, protein and lipid contents of the food ingested and their absorption in the intestine of Sarotherodon melanotheron inhabiting Awba lake in Ibadan, Nigeria, were investigated. Total carbohydrates of the ingested food ranged from 39.33 to 55.38% (mean = 48.70% while total protein and total lipid ranged from 10.10 to 17.13% (mean = 12.91%) and 7.79 to 8.96% (mean = 8.28%) dry weight, respectively. Calculated total percentages absorbed were 54.86-62.01 (mean 58.07) carbohydrates 47.33-54.06 (mean = 50.43) protein and 43.27-52.23% (mean 46.56) lipid. Absorption of protein and carbohydrate occurred mostly in the fore-gut (the first one-third of the intestine), while lipid was mostly absorbed in the mid-gut (the second one-third of the intestine). Dietary carbohydrate, protein and lipid contents of the food as well as the absorptive capacity of the intestine for these components of the food varied with size of fish

Coastal plant growth and CO2 enrichment: Can the productivity of black needle rush keep pace with sea level rise?

The rate of sea level change has varied considerably over geological time, with rapid increases (0.25 cm yr-1) at the end of the last ice age to more modest increases over the last 4,000 years (0.04 cm yr-1; Hendry 1993). Due to anthropogenic contributions to climate change, however, the rate of sea level rise is expected to increase between 0.10 and 0.25 cm year-1 for many coastal areas (Warrick et al. 1996). Notwithstanding, it has been predicted that over the next 100 years, sea levels along the northeastern coast of North Carolina may increase by an astonishing 0.8 m (0.8 cm yr-1); through a combination of sea-level rise and coastal subsidence (Titus and Richman 2001; Parham et al. 2006). As North Carolina ranks third in the United States with land at or just above sea level, any additional sea rise may promote further deterioration of vital coastal wetland systems. (PDF contains 4 pages)

Mortality, growth and growth rate variability of striped bass larvae in Chesapeake Subestuaries

In this report we develop age-length keys and derive age-frequency data. We estimate striped bass and white perch mortality and growth rates, based on the otolith-aging analysis. We also report on hatch-date frequencies of striped bass and white perch larvae, and we discuss environmental effects on recruitment potential.

Effects of suspended sediments on the development of eggs and larvae of striped bass and white perch

The possible ecological effects of suspended sediments are manifold. Briefly, suspended sediments may cause an increased surface for microorganism growth, fewer temperature fluctuations, chemical adsorption or absorption, blanketing, mechanical-abrasive actions, and light penetration reduction (Cairns, 1968). Sherk and Cronin (1970) have pointed out that the above effects have been little studied in the estuarine environment. The ecological effects of suspended sediments on fish eggs and larvae may be of prime importance t o the C and D Canal area, an important spawning and primary nursery area for a variety of estuary: e species (Johnson,1972). This section discusses the effects of suspended sediment on the eggs and larvae of striped bass and white perch.

Eggs, Larvae and Young of The Striped Bass, Roccus saxatilis

Detailed descriptions of the early development of the striped bass, Roccus saxitilis (Walbaum), with emphasis on variation in size and morphology, sequence of fin formation, changes in body form, and attainment of the full complement of maristic numbers, are presented and illustrated for the first time. The egg is spherical, transparent, non-adhesive and relatively large. It is pelagic and buoyant, although it sinks in quiet fresh water. When unfertilized, it averages 1.3 mm, in diameter, but is 3.4 mm. when fertilized and water-hardened. The granular yolk sac, green when alive and whitish-yellow when preserved, averages 1.2 mm., and the single amber-colored oil globule is about 0.6 mm. in diameter. Newly hatched striped bass prolarvae, which range from 2.9-3.7 mm. in total length, are relatively undeveloped and nearly transparent, with no mouth opening, unpigmented eyes, and a greatly enlarged yolk sac with the large oil globule projecting beyond the head. When 5-6 mm. long the yolk sac and oil globule are assimilated and the postlarvae I show advanced development of the internal anatomy. Although the fish is still transparent, scattered melanophores are found on the head and body and chromatophores in the eyes and the ventro-posterior edge of the body. Postlarvae transform to young between 7 and 10 mm. in length when the finfolds are lost except in the dorsal, anal and caudal regions. The largest fish in this group possess a well-formed skeleton with a full complement of 25 vertebrae. Between 10 and 20 mm. in length all fish are fully transformed, muscular tissue renders most of the internal structure obscure, and the myotomes, which generally correspond in number with the vertebrae, are no longer visible. At fish lengths of 20-30 mm. scales are found on all specimens, and with the exception of the pectoral fin-rays, a full complement of meristic structures is present in all other fins. At this stage the body is pigmented uniformly with small spots. Linear regressions between several dependent variables and the , independent variable of standard length indicate that the rate of development of head, eye. and snout to anus lengths is proportional to the length of the larvae and young. Body depth and standard length are non-linear among newly-hatched larvae. Hatchery-reared striped bass demonstrated a slow rate of growth, and were regarded as "stunted," when compared to growth rates observed in another study and field collections. Observations were also made on abnormal eggs and teratological larvae and young. Blue-sac disease is tentatively identified and described for the first time in larvae and pugnosed larvae and young are also described for the first time in striped bass.

Development of trophic state and phytoplankton in an oligo-mesotrophic reservoir (Kleine Kinzig) in Black Forest, Germany

Since 1989, intensive studies have been made on a relatively new (1983-84) oligotrophic reservoir and its pre-reservoir in the Black Forest. This paper briefly reports on the hydrochemistry, especially annual variations in phosphorus loadings, and the seasonal development of phytoplankton in 1989 and 1990.

Fecundity estimates for Maryland Striped Bass

Contemporary striped bass population modeling efforts on coastal stocks point to a reduced population fecundity in Chesapeake Bay being partially responsible for declining reproduction (Anonymous 1985; Boreman and Goodyear 1984). Fecundity values used in these models were based on earlier work by jackson and tiller (1952), lewis and Bonner (1966), Hollis (1967) and Holland and Yelverton (1973). An important feature to the Boreman and Goodyear (1985) model (FSIM) is an accurate determination of the fecundity weight regression equation used to determine the rate of egg deposition over time. Egg deposition models in turn can be used to determine how reproductive potential is changing over time in response to various management actions, i.e. reducing fishing mortality rates. thus it is imperative to follow population stock structure in the Bay system and to develop a contemporary fecundity relationship for striped bass. This report deals with the gonadal material collected in 1986 and 1987 from a coordinated Maryland field program. Samples were obtained from drift gill net collections during the spawning season from four localities: Potomac Estuary, Upper Bay, Chesapeake and Delaware Canal, and the Choptank Estuary (Figure 1).

Distribution, movements, and habitat use of small striped bass (Morone saxatilis) across multiple spatial scales

Distribution, movements, and habitat use of small (<46 cm, juveniles and individuals of unknown maturity) striped bass (Morone saxatilis) were investigated with multiple techniques and at multiple spatial scales (surveys and tag-recapture in the estuary and ocean, and telemetry in the estuary) over multiple years to determine the frequency and duration of use of non-natal estuaries. These unique comparisons suggest, at least in New Jersey, that smaller individuals (<20 cm) may disperse from natal estuaries and arrive in non-natal estuaries early in life and take up residence for several years. During this period of estuarine residence, individuals spend all seasons primarily in the low salinity portions of the estuary. At larger sizes, they then leave these non-natal estuaries to begin coastal migrations with those individuals from nurseries in natal estuaries. These composite observations of frequency and duration of habitat use indicate that non-natal estuaries may provide important habitat for a portion of the striped bass population.

Analysis of permanent magnets as elasmobranch bycatch reduction devices in hook-and-line and longline trials

Previous studies indicate that elasmobranch fishes (sharks, skates and rays) detect the Earth’s geomagnetic field by indirect magnetoreception through electromagnetic induction, using their ampullae of Lorenzini. Applying this concept, we evaluated the capture of elasmobranchs in the presence of permanent magnets in hook-and-line and inshore longline fishing experiments. Hooks with neodymium-iron-boron magnets significantly reduced the capture of elasmobranchs overall in comparison with control and procedural control hooks in the hook-and-line experiment. Catches of Atlantic sharpnose shark (Rhizoprionodon terraenovae) and smooth dogfish (Mustelus canis) were signif icantly reduced with magnetic hook-and-line treatments, whereas catches of spiny dogfish (Squalus acanthias) and clearnose skate (Raja eglanteria) were not. Longline hooks with barium-ferrite magnets significantly reduced total elasmobranch capture when compared with control hooks. In the longline study, capture of blacktip sharks (Carcharhinus limbatus) and southern stingrays (Dasyatis americana) was reduced on magnetic hooks, whereas capture of sandbar shark (Carcharhinus plumbeus) was not affected. Teleosts, such as red drum (Sciaenops ocellatus), Atlantic croaker (Micropogonias undulatus), oyster toadfish (Opsanus tau), black sea bass (Centropristis striata), and the bluefish (Pomatomas saltatrix), showed no hook preference in either hook-and-line or longline studies. These results indicate that permanent magnets, although eliciting species-specific capture trends, warrant further investigation in commercial longline and recreational fisheries, where bycatch mortality is a leading contributor to declines in elasmobranch populations.

Diel and seasonal timing of sound production by black drum (Pogonias cromis)

Acoustic recorders were used to document black drum (Pogonias cromis) sound production during their spawning season in southwest Florida. Diel patterns of sound production were similar to those of other sciaenid fishes and demonstrated increased sound levels from the late afternoon to early evening—a period that lasted up to 12 hours during peak season. Peak sound production occurred from January through March when water temperatures were between 18° and 22°C. Seasonal trends in sound production matched patterns of black drum reproductive readiness and spawning reported previously for populations in the Gulf of Mexico. Total acoustic energy of nightly chorus events was estimated by integration of the sound pressure amplitude with duration above a threshold based on daytime background levels. Maximum chorus sound level was highly correlated with total acoustic energy and was used to quantitatively represent nightly black drum sound production. This study gives evidence that long-term passive acoustic recordings can provide information on the timing and location of black drum reproductive behavior that is similar to that provided by traditional, more costly methods. The methods and results have broad application for the study of many other fish species, including commercially and recreationally valuable reef fishes that produce sound in association with reproductive behav

Use of non-natal estuaries by migratory striped bass (Morone saxatilis) in summer

For most migratory fish, little is known about the location and size of foraging areas or how long individuals remain in foraging areas, even though these attributes may affect their growth, survival, and impact on local prey. We tested whether striped bass (Morone saxatilis Walbaum), found in Massachusetts in summer, were migratory, how long they stayed in non-natal estuaries, whether observed spatial patterns differed from random model predictions, whether fish returned to the same area across multiple years, and whether fishing effort could explain recapture patterns. Anchor tags were attached to striped bass that were caught and released in Massachusetts in 1999 and 2000, and recaptured between 1999 and 2007. In fall, tagged striped bass were caught south of where they were released in summer, confirming that fish were coastal migrants. In the first summer, 77% and 100% of the recaptured fish in the Great Marsh and along the Massachusetts coast, respectively, were caught in the same place where they were released. About two thirds of all fish recaptured near where they were released were caught 2–7 years after tagging. Our study shows that smaller (400–500 mm total length) striped bass migrate hundreds of kilometers along the Atlantic Ocean coast, cease their mobile lifestyle in summer when they use a relatively localized area for foraging (<20 km2), and return to these same foraging areas in subsequent ye

Use of pop-up satellite archival tag technology to study postrelease survival of and habitat use by estuarine and coastal fishes: an application to striped bass (Morone saxatilis)

Pop-up satellite archival tags (PSATs) have been used to study movements, habitat use, and postrelease survival of large pelagic vertebrates, but the size of these tags has historically precluded their use on smaller coastal species. To evaluate a new generation of smaller PSATs for the study of postrelease survival and habitat use of coastal species, we attached Microwave Telemetry, Inc., X-tags to ten striped bass (Morone saxatilis) 94–112 cm total length (TL) caught on J hooks and circle hooks during the winter recreational fishery in Virginia. Tags collected temperature and depth information every five minutes and detached from the fish after 30 days. Nine of the ten tags released on schedule and eight transmitted 30% to 96% (mean 78.6%) of the archived data. Three tags were physically recovered during or after the transmission period, allowing retrieval of all archived data. All eight striped bass whose tags transmitted data survived for 30 days after release, including two fish that were hooked deeply with J hooks. The eight fish spent more than 90% of their time at depths less than 10 m and in temperatures of 6–9°C, demonstrated no significant diel differences in depth or temperature utilization (P>0.05), and exhibited weak periodicities in vertical movements consistent with daily and tidal cycles.

Effects of rapid decompression and exposure to bright light on visual function in black rockfish (Sebastes melanops) and Pacific halibut (Hippoglossus stenolepis)

Demersal fishes hauled up from depth experience rapid decompression. In physoclists, this can cause overexpansion of the swim bladder and resultant injuries to multiple organs (barotrauma), including severe exophthalmia (“pop-eye”). Before release, fishes can also be subjected to asphyxia and exposure to direct sunlight. Little is known, however, about possible sensory deficits resulting from the events accompanying capture. To address this issue, electroretinography was used to measure the changes in retinal light sensitivity, flicker fusion frequency, and spectral sensitivity in black rockfish (Sebastes melanops) subjected to rapid decompression (from 4 atmospheres absolute [ATA] to 1 ATA) and Pacific halibut (Hippoglossus stenolepis) exposed to 15 minutes of simulated sunlight. Rapid decompression had no measurable influence on retinal function in black rockfish. In contrast, exposure to bright light significantly reduced retinal light sensitivity of Pacific halibut, predominately by affecting the photopigment which absorbs the green wavelengths of light (≈520–580 nm) most strongly. This detriment is likely to have severe consequences for postrelease foraging success in green-wavelength-dominated coastal waters. The visual system of Pacific halibut has characteristics typical of species adapted to low light environments, and these characteristics may underlie their vulnerability to injury from exposure to bright light.