Aspects of the reproductive biology of the grouper, Epinephelus tauvina (Forskål), in Kuwaiti waters

Gonad maturation in Epinephelus tauvina is examined over one annual reproductive cycle. The species has one major spawning period from April to May and this is associated with increasing water temperatures and relatively low salinity. The histological changes in the gonads in the female, male and transitional phase are examined, and oogenesis and spermatogenesis are described in five developmental stages. That E. tauvina is a protogynous hermaphrodite is confirmed, and sexual transition is found to occur in individuals 55–75 cm in length, and is related to spawning activity. Fecundity estimates for E. tauvina of length 35.1–62.3 cm ranged from 850 186 to 2 904 921.     

AGE STRUCTURE AND GROWTH OF THE BOTTLENOSE DOLPHIN (TURSIOPS TRUNCATUS) FROM STRANDINGS IN THE MISSISSIPPI SOUND REGION OF THE NORTH-CENTRAL GULF OF MEXICO FROM 1986 TO 2003

Despite their high abundance and wide distribution, little is known about the historical or current growth and age structure of coastal bottlenose dolphins ( Tursiops truncatus ) in the north-central Gulf of Mexico. Between 1986 and 2003, teeth were collected from bottlenose dolphins stranded on the mainland coast of Mississippi and the adjacent barrier islands. Bottlenose dolphin strandings occurred year round, peaking in March and April. Neonate strandings also peaked during these 2 mo. Age estimates were obtained from 111 animals by reading the growth layer groups in the dentine layer of the teeth. The ages ranged from <1 yr to 30 yr of age. The two-stage Laird–Gompertz growth model was fitted to the total length and age data. On the basis of this model, the asymptotic lengths were estimated at 250 cm for females and 255 cm for males. The length at birth estimates were 98–103 cm for females and 100–107 cm for males. These lengths are similar to those of bottlenose dolphin populations from other Gulf of Mexico areas and from the North Atlantic Ocean along the southeastern United States.     

Habitat selection by grayling—I. Spawning habitats

Grayling spawning sites were investigated in two French rivers, the Pollon (1 year) and the Suran (2 years) and described by current velocity, water depth, and substrate composition, completed by an assessment of bottom shear stress with FST-hemispheres. A comparison was made between used and available habitats, the latter being characterized by random sampling of 300 m long (Pollon) and 510 m long (Suran) river sections, both including three riffle/pool sequences. Mean velocities observed on spawning sites did not differ significantly between rivers or years (overall mean 48–9 cm s^-1 S.D. = 11.9, range 25.8–91.7 cm s^-1, n =150). Most water depths ranged from 10 to 40 cm in both rivers, but mean depths were significantly different ( P <0.05). Substratum of spawning grounds was dominated by gravel and pebbles (2–64 mm) in both rivers. Most spawning sites (99%) were characterized by a narrow range of hemispheres (nos 9–13), i.e. a range of shear stress of about 5–16 dyn m^-2. In the Pollon, spawners between spawning acts were found in a resting pool located immediately downstream from the spawning area and characterized by slow-flowing water (mainly <20 cm s^-1) and great depth (mainly >60 cm), with cover provided by overhanging branches and tree roots.     

A biological analysis of eel catches, Anguilla anguilla L., from the lagoons of Lesina and Varano, Italy

A study of eel catches from Lesina (444 specimens) and Varano lagoons (325 specimens), in southern Adriatic, Italy, was made. Male silver eels in Lesina ranged from 33.4–51.5 cm in length, with a mean of 42.6 cm; from 50–240 g in weight, with a mean of 141 g and were 1.5–6.5 years old with a mean of 2.5 years. The average length of male silver eels in Varano lagoon was 40.5 cm (range 31–48.5 cm); the average weight was 122 g (range 80–220 g)and a mean age of 2.6 years (range 1.5–7.5 years).
The females are bigger, heavier and older than the males with, in Lesina, a mean length of 61 cm (range 50.9–74.3 cm), a mean weight of 438 g (range 240–730 g) and a mean age of 3.4 years (range 1.5–6.5). The average length of Varano female silver eels was 58 cm (range 50.8–72.5 cm), and the average weight was 383 g (range 225–840 g). They were 1.5–7.5 years old, with an average of 3.8 years. Female silver eels were only 20% of the population at Lesina and 10% at Varano.
In comparison with the silver eel populations of the North Adriatic lagoons, the North Sea or the Atlantic Ocean, the silver eels of Lesina and Varano show a greater growth rate, are younger and have a sex ratio in favour of the males.
The water temperature, higher than in other countries, could be an important factor affecting the differences in age and growth rates between Lesina and Varano silver eels and those of other waters.     

Gastric evacuation rates and daily ration of piscivorous coho salmon, Oncorhynchus kisutch Walbaum

Effects of temperature and meal size on gastric evacuation rates of juvenile coho salmon, Oncorhynchus kisutch , consuming sockeye salmon, O. nerka , fry were examined and used in the estimation of daily meal, daily ration and number of fry consumed by coho in Chignik Lake, Alaska. Evacuation of fry by coho was best described by a negative exponential model (average R² = 0.93). A square root model also provided a good fit (average R² = 0·93), but the y-intercepts deviated more from the expected value than did the y-intercepts of the exponential model. The effect of temperature ( T , 5–13° C) and meal size (MS, 0·166–0·367 g) on the exponential evacuation rate (r_e, h^-1) could be described as
In the lake, coho fed continuously during the 24-h period in early June 1986 and 1987. Estimates of daily meal and ration of coho calculated by the Eggers method and the geometric mean of prey weight ranged from 0·224 to 0·435 g (2.1–4.4% body wt) depending on location and year. The Elliott & Persson method provided similar estimates of food consumption, whereas estimates based on the Pennington method and square root evacuation of prey differed from the exponential models. Sockeye fry represented 93% of the total prey weight. The average number of sockeye fry consumed per coho per 24 h, based on the arithmetic mean of prey weight, was 3·0–3·9 fry.     

Age estimation of the exploited deepwater shark Centrophorus squamosus from the continental slopes of the Rockall Trough and Porcupine Bank

Dorsal spine sections of the deepwater squalid shark Centrophorus squamosus provided age estimates of 21–70 years. Small specimens were not recorded in the study area. It was not possible to obtain estimates from vertebral centra. The estimates are discussed in the context of other studies using dorsal spines of squalid sharks. Sexual maturity was achieved at large size, >75% of maximum length. Total length at 50% maturity was calculated as 101 cm (males) and 128 cm (females).     

Polystoma cuvieri n. sp. (Monogenea: Polystomatidae), a parasite of the urinary bladder of the leptodactylid frog Physalaemus cuvieri in Paraguay

A new species of polystomatid monogenean, Polystoma cuvieri, is described from the urinary bladder of the leptodactylid frog Physalaemus cuvieri Fitzinger in Paraguay. This new species possesses a reticulated intestine and hamuli of about 350 microns long. The closest species is Polystoma napoensis Vaucher, 1987, described from Osteocephalus spp. in Ecuador. The Paraguayan material is distinguished by the blade size of the hamuli. The hamuli blades appear to be useful in Polystoma systematics.     

An application of the plaster dissolution method for quantifying water velocity in the shallow hyporheic zone of an Appalachian stream system

1. A method for quantifying interstitial water velocity based on the dissolution rate of plaster of Paris standards was developed as part of a study of vertical, longitudinal (1–4 order sites) and seasonal variation in the biotic and physical characteristics of the shallow hyporheic zone (0–30 cm) of a headwater stream system in West Virginia, U.S.A.
2. A calibration model was developed using a water velocity simulation tank to relate mass loss of plaster standards to water velocity and temperature. The model was then used to calculate water velocity through artificial substrata embedded in the shallow hyporheic zone of four stream reaches based on in situ mass loss of plaster standards.
3. Water velocity in the hyporheic zone increased with stream order, was highest in early spring and winter during high stream base flows, and decreased with depth into the substratum. There was a strong interaction between depth and season: during periods of high stream discharge, water velocity through the upper level of the shallow hyporheic zone (0–10 cm into the substrate) increased disproportionately more than velocity at greater depths. Mean interstitial velocity in March ranged from 0 cm s^–1 in the lowest level (20–30 cm) to 3.5 cm s^–1 at the upper level (0–10 cm) at the first‐order site, and from 2.5 cm s^–1 (20–30 cm) to 9.5 cm s^–1 (0–10 cm s^–1) at the fourth‐order site. Gradients in stream discharge and sediment permeability accounted for treatment effects.
4. Use of calibrated data improved the ability to resolve among‐season differences in interstitial water movement over the use of uncalibrated mass loss data. For some applications of the plaster standard method, empirical calibration may not be necessary.     

Distribution and reproduction of the southern lantern shark from New Zealand

Distribution, population structure and reproduction are described for the southern lantern shark Etmopterus granulosus at the Chatham Rise, New Zealand. Depth of capture for E. granulosus ranged from 744 to 1420 m, with highest catch rates between 800–1200 m. More than twice as many females as males were captured, and the majority of sharks caught were mature, indicating that there may be segregation according to sex and size class. Only 10 of 492 female sharks captured contained ova in uteri, and none contained embryos. The absence of pregnant females suggests that they move to another area or depth prior to pupping. Size of sharks captured ranged from 20·0 to 78·8 cm total length. Females began to mature at 62 cm total length, and males at 52 cm. There was no evidence of a seasonal reproductive cycle. Ovulation appeared to occur when ova reached a diameter of 40–45 mm. The average number of ova in mature females was 12·7. This information is crucial for assessing the impact of fisheries on E. granulosus populations.     

A New Eurypterid (Chelicerata: Eurypterida) from the Upper Devonian Gogo Formation of Western Australia, With A Review of the Rhenopteridae

A new eurypterid, Rhenopterus waterstoni sp. nov., is described from the Gogo Formation (Frasnian, Upper Devonian) of Western Australia. This species is distinguished from related forms by the tuberculation of the anteriormost tergite and crenulated posterior margins of the carapace and opisthosomal segments. It is the only eurypterid specimen known from the Gogo Formation, the most complete eurypterid from Australia, and also the youngest representative of Rhenopterus in the fossil record. Structures retrieved from between the prosomal-opisthosomal juncture comprise polygonal tubes 30–40 μm in diameter, which are interpreted as sarcomeral sheaths of muscular tissue. Rhenopterus is reviewed: R. latus Størmer, 1936 is synonymized with R. diensti Størmer, 1936 as it is here recognized as a female sexual dimorph; R. maccarthyi (Kjellesvig-Waering, 1934) is an orthocone nautiloid.     

Wood decomposition in an abandoned beech and oak coppiced woodland in SE England

The rate of litter decomposition is often expressed as a constant decay rate (k; g g⁻¹ yr⁻¹) or as the time required for a certain percentage (often 95% and estimated as 3/k) of it to decompose (termed turnover time). Estimates of k may be obtained by determining the weight loss of litter in the field and also by assuming a steady state and obtaining the ratio of litter input: standing crop. Both methods were used to estimate decay rate and turnover times for beech and oak branches and twigs decomposing on the forest floor and these were critically evaluated.
Considerable variation, ranging between 1.8–144.5 yr, was found between the 95% turnover time estimates of various size components of the two species, obtained from woodfall and standing crop data. Likewise variation in decay rate of 2–2.5 cm diameter beech branches, estimated from field experiments, was large both between and within groups of branches categorised according to initial state of decay and presence or absence of bark. The mean annual decay rate for the various categories ranged between k = 0.165-0.452 g g⁻¹yr⁻¹. Branches without bark generally decomposed more slowly than those with bark. Beech twig (<0.5 cm diameter) decomposition rates, from field experiments, ranged between k = 0.149-0.220 g g⁻¹yr⁻¹ and variation was relatively low compared with that of branches. No significant differences (P<0.05)were detected between twig decomposition rates obtained from experiments initiated at different seasons although there was a slight decline in decay rate in winter months. Twig and branch decomposition rates fell within the range found in the few other comparable studies.     

Effect of temperature on larval growth of Ecdyonurus dispar (Ephemeroptera: Heptageniidae) from two English lakes

SUMMARY. Mature larvae of Ecdyonurus dispar were collected from Ennerdale Water and Windermere (English Lake District) and reared to adult males and females in the laboratory. The females were then fertilized artificially and their progeny were kept at constant temperatures (range 4.2–20.2°C). Larvae collected directly from the two lakes were also reared under the same conditions.
The maximum number of instars from egg to subimago was 25, the average body length increment (mm) per moult was proportionately constant at c . 15% and Dyar's rule was applicable. The interval between moults decreased with increasing temperature and the relationship between the two variables within the temperature range 4.2–19.8°C was described by a power law. Larval growth was exponential and variations in mean specific growth rate (range 0.23–5.23% length day⁻¹) were related to mean temperature which was the major factor affecting growth in the laboratory. A few experiments were also performed in the lake to test the adequacy of the estimated values for larval growth at different temperatures in the laboratory. There was agreement between the estimates and the actual growth rates in the lake. Therefore, the regression equations obtained from the laboratory experiments are probably applicable to larval growth in the field.
Values for daily production in the laboratory ranged from 0.53 to 9.33 mg dry wt day⁻¹ m⁻². The lowest value was obtained at 8.9°C and the highest at 20°C.
Information on different life cycles of E. dispar is briefly reviewed and it is concluded that E. dispar from the lakes can only achieve one generation per year.     

Comparison of field-based and indirect estimates of daily food consumption in larval perch and zander

Since bioenergetics models for 0+ fish have seldom been validated by field consumption estimates, field-based and indirectly estimated daily food rations were compared in larval perch Perca fluviatilis and zander Stizostedion lucioperca. Field-based estimates were calculated with linear and exponential evacuation rates based on gut fullness data during a 24-h cycle, with hourly field samplings instead of the normally recommended 3-h intervals. Indirect calculations used bioenergetics modelling with variable activity multipliers ( A ). Field-based estimates of daily rations ranged between 0·21 and 0·27 g g⁻¹ day⁻¹ in perch (mean L _T 13·1 mm) and 0·31–0·40 g g⁻¹ day⁻¹ in zander (mean L _T 10·6 mm). The higher values were calculated by using the exponential model. Daily rations calculated by bioenergetics modelling with A = 1 were only slightly higher than direct estimates in both species. However, if A values >1 were used, calculated daily rations were substantially higher than direct estimates. Estimates of daily ration based only on every third value ranged between 41 and 72% compared with 1-h intervals, mainly because of lower estimates of evacuation rate.     

An in situ estimate of daily food consumption and alimentary canal evacuation rates of common carp, Cyprinus carpio L.

Daily food consumption and alimentary canal evacuation rates for common carp, Cyprinus carpio L., were estimated at 4-week intervals from April to October 1979. Both the rate of food evacuation and its relationship to temperature were described by an exponential function. Gut evacuation rates ranged from 6.0% of gut contents per hour at 9°C to 32.7% h⁻¹ at 26.5°C. Temperature accounted for 72–91% of the variation in gut evacuation rate among months. Daily food consumption varied from a low of 3.87 mg g⁻¹ of fish wet wt per day in April at 14°C (0.39% of wet body wt) to a high of 40.75 mg g⁻¹ (4.08%) in August at 26.5°C. Although a greater quantity of food appeared to be consumed during the morning in spring and early summer and a greater amount in the evening after July, there was not a statistically significant time of day for peak feeding activity. The field method described here seemed to provide reasonable estimates of food consumption compared with other field and laboratory studies.     

Influence of water depth on dispersion of juvenile salmonids, Salmo salar L. and S. trutta L., in a Scottish stream

The dispersion of salmon and trout of 0 +, 1 + and 2 + age classes was examined by electrofishing 12 sections of a stream in Perthshire, Scotland at the end of the growing season in September to October in 1972 and 1976. In 1972 sections ranged in surface area from 21 to 122 m² and had volumes of 5.0–17.3 m³ and when surveyed in 1976 surface areas were 15–106 m² and volumes 2.1–6.7 m³. In 1976 widths and areas of sections were 63–87% of the values for 1972, depths were 39–68% and volumes 28–52% of the earlier values. These differences were due to 1976 being drier and warmer. In both years, all sections contained 0 + and 1 + age classes of salmon and trout and some sections contained 2 + age salmon and trout. The total density of fish in a section ranged from 1.9 to 3.9 m⁻² in 1972 and from 3.72 to 6.08 m⁻² in 1976. There was an inverse relationship, significant in 1972 only, between the density of 0 + salmon and that of 1 + trout in the different sections. Densities of both 0 + and 1 + salmon in the sections were inversely correlated, and those of 0 + and 1 + trout were directly correlated, with area of water deeper than 10 cm.     

Reproduction of the summer flounder, Paralichthys dentatus (L.)

The reproduction of summer flounder, Paralichthys dentatus (L.), occurring in the Middle Atlantic Bight was studied from 1974–1979. Males dominated the length interval between 21–35 cm t.l. and were essentially absent in samples >55 cm t.l. Females were more abundant in all length intervals >45 cm t.l. Length at maturity ranged from 24–27 cm t.l. for males and from 30–33 cm t.l. for females which coincided with length at age two. Ovarian egg diamerter frequencies indicated summer flounders are serial spawners and the trend in mean and maximum maturity indexes (% ovary weight of total fish weight) indicated spawning began in September and continued through February in 1975 and probably into March in 1976. Annual condition cycle of males peaked in September and was lowest in April while females' cycle reached a maximum in October which coincided with peak spawning time. Fecundity was related to length, weight and ovary weight for 1974–1977 and the length-fecundity equation F = 0.0007975 L ^3.402 was found to be the best predictive relationship. The overall reproductive strategy of summer flounder was discussed and apparently tends to maximize reproductive potential through an extended spawning season, early maturation, high fecundity, serial spawning and extensive spawning migrations.     

Age estimation, growth, maturity and distribution of the roundnose grenadier from the Rockall trough

This paper summarizes the history of commercial exploitation of roundnose grenadier Coryphaenoides rupestris in the North Atlantic. Length frequencies of C. rupestris in 1993, from 400 to 1200 m on the slopes of the Rockall trough indicate a reduction since the 1970s in the modal length of fish found at 700–1000 m. Ages ranged from 2 to 50 years for males and 2 to 60 years for females, with most between 10–38 years. Females attained a greater asymptotic pre-anus length ( L _∞=19.5 cm) than males ( L _∞=15.5 cm) and had a greater weight for a given age (male W _∞=761g, female W _∞=1132g). This species may have a protracted spawning period. Using pre-anus lengths, 50% of male fish were mature at 10 cm (ages 8–10) while 50% of female fish were mature at 12 cm (ages 9–11). At the greatest depths sampled the length frequency of fish was bimodal with a hiatus between 9 and 11 cm (ages 8–12). Highest catch rates occurred on the Donegal slope in September at a depth of 800–1000 m.     

MICROVERTEBRATE BIOSTRATIGRAPHY OF UPPER DEVONIAN (FRASNIAN) CARBONATE ROCKS IN THE CANNING AND CARNARVON BASINS OF WESTERN AUSTRALIA

Abstract:  Shark teeth and scales from the Gneudna Formation type section, Carnarvon Basin are rare, but they represent a diverse fauna as well as being the first Frasnian chondrichthyan remains found in Western Australia. In contrast numerous shark teeth and scales have been obtained from coeval sections in the Canning Basin. Teeth referred to as Phoebodus bifurcatus, Phoebodus fastigatus, Phoebodus cf. fastigatus, Phoebodus latus , Phoebodus sp. C and Protacrodus sp. 1 are described from two Canning Basin localities: Horse Spring Range and McIntyre Knolls. The phoebodont species described here have a global distribution and can, therefore, be placed within the standard Frasnian phoebodont zonation. The shark remains from the Gneudna Formation type section include one new genus Emerikodus ektrapelus gen. et sp. nov., described along with Helodontidae indet and Elasmobranchii gen. et sp. indet. It is proposed that the faunal differences observed between the localities are a result of environmental differences. In addition to shark remains, scales from the thelodont Australolepis seddoni were also recovered from each locality. The well-dated Zone 6–10 conodont faunas at Horse Spring constrain the range of A. seddoni with which they occur, and importantly indicate that the Gneudna Formation type section is wholly Frasnian.     

Geographic patterns of genetic variation in four Neotropical rodents: conservation implications for small game mammals in French Guiana

The Neotropics contributes significantly to global biodiversity yet little is known about its mammalian fauna. Given our limited knowledge, concerns are that extinctions at the local level may cause a decline in genetic diversity through the loss of unique alleles. Here we report the geographical population structure of four rodent species from French Guiana: Dasyprocta leporina , Agouti paca , Proechimys cayennensis and P. cuvieri . Two of them ( Dasyprocta and Agouti ) are commonly harvested throughout the country for subsistence and/or game hunting. Cytochrome b and control region sequences revealed the presence of a number of maternal lineages occurring in sympatry throughout French Guiana. We applied two cytochrome b rodent clock calibrations (7.5% and 12% per million years) to our data, and placed the divergence of the maternal lineages to between 160 000 and 260 000 years ago for the more diverse D. leporina and P. cuvieri , and between 66 000 and 46 000 years ago for the more recent A. paca and P. cayennensis . The clades appear to be widespread throughout South America as indicated by specimens sampled in Brazil, Peru, and Venezuela. At the population level, AMOVA revealed little or no geographical structure within French Guiana. However, this conclusion is based on a single genetic marker and relatively few specimens.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 81 , 203–218.     

Growth, biomass yield and biomass functions for plantation-grown Nauclea diderrichii (de wild) in the humid tropical rainforest zone of south-western Nigeria

Adequate management of forest plantation requires estimation of growth and biomass yield and consequently, the fitting of functions for estimating biomass. Growth, biomass yield and biomass functions for estimating biomass of Nauclea diderrichii plantations in Omo forest reserve, Nigeria are described. Data were obtained from 30 temporary sample plots selected from stands that are 5-30 years old. A total of 81 trees were harvested for biomass estimation. Mean tree diameter at breast height (dbh), total height and stand bole volume ranged from 9.6 to 29.3 cm; 9.0 to 23.6m and 23.27 to 535.52 m(3)ha(-1), respectively while Total Above Ground Biomass (TAGB) varied from 32.5 t ha(-1) to 287.5 t ha(-1) between 5 and 30 years. Biomass allocations to stem, branch and foliage were 84.5%, 13.5% and 3%, respectively. All biomass components could be described precisely by dbh alone (R(adj)(2)>0.97), with very low standard errors of estimates. Little improvement in the precision of the functions was achieved by including total height. In addition, the residuals of regression functions with only dbh were generally more constrained than those that included total height. Consequently, the functions with dbh alone and its derivative as independent variables were recommended for estimating biomass of opepe in Nigeria.