Fecundity of the American eel Anguilla rostrata at 45° N in Maine, U.S.A.

The northern portion of the geographic range of the American eel Anguilla rostrata may contribute a great proportion of the reproductive potential to this panmictic species because of apparent increases in average female size and female percentage with latitude. The regressions of fecundity on body length and on body weight of 63 female eels captured at about 45° N latitude on their spawning migration to the sea were log F= 1·2601 + 2·9642 log L and log F= 4·1646+0·9153 log W , where F is fecundity, L is total length (cm), and W is total weight (g). Length and weight each explained about 90% of the variation in fecundity. Estimates of fecundity from counts of aliquots of eggs ranged from 1·84 million to 19·92 million eggs for eels ranging in length from 45 to 113 cm, nearly the range of sizes of migrating females reported in the literature. Fecundities of the American eel were greater than reported in one study at about 37° N and greater than reported for the European eel, A. anguilla , shortfin eel, A. australis , and longfin eel, A. dieffenbachii . If a geographic cline in fecundity does exist in American eels, it is established anew each generation because the species forms a single panmictic population.     

Reproductive biology of Tilapia zillii (Gervais) in Lake Naivasha,Kenya

Synopsis Tilapia zillii breeds all year round in the equatorial Lake Naivasha with slightly high breeding intensity during wet months (March, May and July–August). A sex ratio of 1 : 1.28 was found between males and females. The smallest mature male and female were 9.0 and 11.0 cm respectively. The fecundity ranged from 2990 to 12344 eggs, with a mean of 6606 eggs. Fecundity showed a curvilinear relationship with total length (log F = 1.7034 + 1.6370 log L) and a linear relationship with body weight (F = 2197 + 28.76 W)     

Determination of age, growth and sexual maturity of Barbus grypus in the Dukan reservoir of Iraq

A total of 317 carp Barbus grypus were collected during one year (1977–1978) from the Dukan reservoir of Iraq to study age, grwoth and sexual maturity. The length-weight relationship was found be: log: W =–4.2298 + 2.6832 log L. and the condition ( K ) was 0.88. Back calculation was determined by using a correction factor (45.727) in Lee's equation. Predicted standard length and weight were found to be less than the actual values. The maximum increase in length was noted in the first year group, while the maximum increase in weight occurred at the time of sexual maturity. Males were found to attain maturity earlier than the females. Spawning took place during May and June.     

The seasonal cycle of condition in the pollan, Coregonus autumnalis pollan Thompson, of Lough Neagh, Northern Ireland

The length–weight relationship for Lough Neagh pollan was log W= 3·2 log L –2·24. Covariance analysis indicated that there were no differences between the sexes, with maturity, or between years. While a seasonal cycle in relative condition was in phase with gonad development during late summer and autumn, changes in somatic condition presented a more complex pattern. Somatic condition increased in spring, as did the quantity and diversity of food consumed. Despite good conditions for feeding and growth, there was an autumn fall in somatic condition, caused by the diversion of energy to gonad growth.     

Energy expenditure during flight in relation to body mass: effects of natural increases in mass and artificial load in Rose Coloured Starlings

Rose Coloured Starlings (Sturnus roseus) flew repeatedly for several hours in a wind tunnel while undergoing spontaneous variation in body mass. The treatments were as follows: flying unrestrained (U), with a control harness of 1.2% of their body mass (C), or with a harness of 7.4% of their body mass, which was either applied immediately before the flight (LS) or at least 9 days in advance (LL). Energy expenditure during flight (ef in W) was measured with the Doubly Labelled Water method. Flight costs in L(S) and LL were not significantly different and therefore were pooled (L). The harness itself did not affect ef, i.e. U and C flights were not different. ef was allometrically related with body mass m (in g). The slopes were not significantly different between the treatments, but ef was increased by 5.4% in L compared to C flights (log10(ef) = 0.050 + 0.47 x log10(m) for C, and log10(ef) = 0.073 + 0.47 x log10(m) for L). The difference in ef between C, LS and LL was best explained by taking the transported mass m transp (in g) instead of m into account (log10(ef) = -0.08 + 0.54 x log10(m transp)). Flight costs increased to a lesser extent than expected from interspecific allometric comparison or aerodynamic theory, regardless of whether the increase in mass occurred naturally or artificially. We did not observe an effect of treatment on breast muscle size and wingbeat frequency. We propose that the relatively low costs at a high mass are rather a consequence of immediate adjustments in physiology and/or flight behaviour than of long-term adaptations.     

Consumption, growth and respiration of bleak, Alburnus alburnus (L.), and roach, Rutilus rutilus (L.), during early ontogeny

Three components of the energy budget, consumption ( C ), production ( P ) and respiration ( R ) in juvenile roach and bleak kept under controlled food ( Anemia salina , 2400 ind. l⁻¹) and temperature (20° C) conditions were measured in a study aimed at defining differences between the two species and elucidating the patterns of energy partitioning during ontogeny.
Daily food consumption rates (J day⁻¹ fish⁻¹) increased allometrically ( C =a W ^b) with body size ( W , mg dry weight) in both species. Covariance analysis indicated no differences in slope or intercept for the two regression lines ( P ≤ 0.05, n = 82). However, the two species grew at significantly different rates, roach faster than bleak.
The dependence of the respiration rate (μmol h⁻¹ fish ⁻¹) on body weight ( W ) can be described by an allometric function: R = a W ^b, where a ± 95% C.L. = 0.17 ± 0.15 for roach and 0.18 ± 0.20 for bleak. The slope for roach (b ± 95% C.L. = 0.78 ± 0.01) is slightly higher than that for bleak (0.69 ± 0.03).
Assimilation efficiency [AE = ( P + R ) C ⁻¹] was significantly higher in roach than in bleak. Different levels of AE correlated with differences in relative gut length (gut length as percentage of body length). Due to the shorter relative gut length above a weight of 5 mg, bleak has lower powers of digestion, which may explain lower production rates. These differences in energetic performance between the two species indicate mechanisms leading to niche differentiation in the early life history of the fishes.     

Biology of the Dragonet, Callionymus kaianus moretonensis Johnson (Pisces:Callionymidae)

A collection in excess of 1000 specimens of Callionymus kaianus moretonensis, trawled off southern Queensland, afforded an opportunity to study various aspects of the biology of this species. It inhabits muddy bottoms at depths of 101–150 m off south-east Queensland between Noosa and Cape Moreton, Moreton Island. Penaeid prawns were the predominant food during all seasons and for all size groups. A great diversity of food items were ingested, especially in the pelecypod and gastropod categories. Factors influencing feeding and vulnerability of prey organisms are discussed. Of the 907 specimens that were sexed, 422 (46.7%) were males and 485 (53.3%) were females. C. k. moretonensis has a prolonged breeding period in which each female spawns a number of times. Only a few oocytes appear to be discharged at any one time from the ovary. Practically every stage of ovarian development was found in each ovary examined regardless of time of year. Oocyte diameter averaged 0.51 mm immediately prior to spawning and numbers of ova ranged from 1285 to 22,478. C. k. moretonensis may have either a benthic larvae or a short-lived planktonic one. Length-weight relationships are represented by the regressions, log W = -1 5.24 + 3.77 log L (males) and log W = -16.77 + 4.12 log L (females). Otoliths were used for age and growth determinations. C. k. moretonensis reaches age group IV+. Growth of males slightly exceeded that of females, with the greatest difference occurring between the third and fourth years of life. No evidence of high post-breeding mortality was found in spent males.     

Red muscle fibre and capillary dimensions in different sizes of a tilapia, Oreochromis niloticus (Trewavas)

Measurements of muscle dimensions that affect respiration in relation to body weight were carried out in a tilapia, Oreochromis niloticus . The fish used in all measurements weighed 0.65–812.3 g. The data were analysed with respect to body weight using logarithmic transformations (log Y=log a + b log W ).
The slopes (b) of the log/log regression lines for weight of body trunk red muscle, average cross-sectional area of muscle fibre, average number of capillaries in direct contact with a muscle fibre, average capillary contact length with a fibre as a fraction of average fibre circumference and number of capillaries mm² of fibre cross-sectional area [N_A(cƒ)] were 1.16, 0.221, 0.084, 0.015, and −0.137 respectively.
These results show that there is an increase in muscle cross-sectional fibre area and number of capillaries in contact with muscle fibres whereas number of capillaries supplying a unit area of muscle fibre decreases during development. There is development of new capillaries with increase in cross-sectional area of red muscle fibres.     

Relationships between Height, Diameter and Weight Distributions of Chenopodium album Plants in Stands: Effects of Dimension and Allometry

Frequency distributions of height (H), stem diameter (D) anddry weight (W) of Chenopodium album plants in even-aged monoculturesat the initial plant densities of 400, 800 and 1200 plants m^-2(400-, 800- and 1200-plots) were compared. The height distributionsat the end of the growing season were bimodal for the 400-plotbut L-shaped for the 800- and 1200-plots. The distributionsof diameter and dry weight were L-shaped for all the plots.When the size measures were expressed on the log scale so asto eliminate effects of the differences in dimension, frequencydistributions of log W and log H for the 400-plot were bimodal.In contrast, the log D distributions were bell-shaped for allthe plots. To elucidate factors responsible for the differences in frequencydistributions among log size measures, we examined allometricrelationships between log size measures. They were all non-linearall non-linear mainly because the allometric relationships weremarkedly different between the plants forming the upper-mostleaf layer ('upper' plants) and the suppressed plants ('lower'plants). A striking feature was that the heights of the 'upper'plants were almost uniform in spite of their varied diameters.Continuous monitoring of growth of the individual plants inthe stand revealed that the height of the 'upper' plants becameuniform just after the canopy closure, at about 30 d after emergence,and that uniform growth in height of these plants continuedfor about 70 d until the end of the growing season. On the otherhand, growth of the suppressed 'lower' plants terminated atvarious stages before flowering. The 'height convergence' ofthe 'upper' plants was thus identified as a key factor for thesegregation of the plants into the two groups of distinctlydifferent allometries. Since the segregation of the plants into 'upper' and 'lower'plants was reflected in their dry weights, frequency distributionsof log W were similar to those of log H. The bell-shaped distributionsof log D were attributed to the overlapping of the diametersof slender 'upper' plants with those of larger 'lower' plants.Significance of 'height convergence' is discussed.Copyright1995, 1999 Academic Press Chenopodium album L., fat hen, height, size structure, bimodal distribution, L-shaped distribution, allometry, growth     

Feeding and growth of early juvenile Japanese sardines in the Pacific waters off central Japan

Larval and early juvenile growth was backcalculated for individual Japanese sardines Sardinops melanostictus using the biological intercept method based on the allometric relationship between otolith radii and fish lengths. Sardines grew at 0·81 mm day⁻¹ during the larval stage. In the early juvenile stage, they grew from 32·3 to 45·4 mm fork length ( L ) over a 20-day period (0·64mm day⁻¹). Using the observed relationship between L and wet body weight ( W ), W = 0·00942 L ^2.99, W of the sardine juveniles was calculated to increase from 306 to 832 mg during the 20-day period. The carbon (C) requirement to achieve this growth in weight was estimated to increase from 5·7 to 9·6 mg day⁻¹. Stomach contents of the sardines were composed mostly of copepods (73%) and larvaceans (25%). Wet stomach content weight ( W_s ) was expressed by a power function of the W , W_s=0·731 W ^0·658. Carbon and nitrogen constituted 41·7 ± 1·5 and 10·0 ± 0·4% of the dry W_s , respectively. Stomach C content increased from 2·0 to 3·9 mg during the 20-day period. Three to four cycles of the daily turnover of stomach contents during the 16 h of daytime, corresponding to a gastric evacuation rate of 0·2–0·3 h⁻¹ under continuous feeding, met the C requirement to achieve the backcalculated growth in early juvenile sardines. The Kuroshio frontal waters seem to provide Japanese sardine juveniles with favourable growth conditions.     

Proposed standard mass equations for European chub Leuciscus cephalus in Italy

Total length (L(T)) and mass measurements of 28,596 specimens of European chub Leuciscus cephalus, collected from a variety of waterways across Italy, were used to compute standard mass (W(s)) equations by both empirical percentile (EmP) and regression line percentile (RLP) methods. The use of the EmP W(s) equation [log(10) W(s) = -4·79 + 2·68log(10) L(T) + 0·10(log(10) L(T))(2)] to compute relative mass (W(r)) of L. cephalus in Italy is suggested, as it was not influenced by length-related bias (L(T) range of application = 70-470 mm).     

Weight loss and sleep-disordered breathing in childhood obesity: effects on inflammation and uric acid

Sleep-disordered breathing (SDB) is prevalent in childhood obesity. It may be an independent risk factor for the metabolic syndrome. Possible mechanisms are inflammation and oxidative stress. Adenotonsillectomy in childhood obesity is associated with a high recurrence rate and risk of postoperative weight gain. Therefore, this study assessed the effects of SDB on inflammation and oxidative stress in childhood obesity before and after weight loss. We included 132 obese subjects between 10 and 18 years consecutively. Median age was 15.4 years (10.1-18.0). Mean BMI z-score was 2.72 ± 0.42. Leukocytes and differentiation, high sensitivity C-reactive protein (hs-CRP), and uric acid (UA) were determined at baseline and subjects underwent a sleep assessment. SDB was diagnosed in 39%. Linear regression analysis showed an association between UA(log) and oxygen desaturation index(log) (ODI(log)) (r = 0.20; P = 0.03), between leukocytes(log) and respiratory disturbance index(log) (RDI(log)) (r = 0.23; P = 0.01), and between lymphocytes(log) and RDI(log) (r = 0.19; P = 0.04). Follow-up was organized after 4-6 months of treatment. Median decrease in BMI z-score was 32%. Laboratory measurements were repeated. Subjects with SDB at baseline underwent a second sleep study. Of these 49 subjects, 12 showed residual SDB. This corresponds with a treatment success rate of 71%. Unlike changes in inflammatory markers, improvements in UA were associated with improvements in RDI and ODI (respectively: r = 0.44; P = 0.007, r = 0.41; P = 0.01). In conclusion, weight loss is effective in treating obese children with SDB. At baseline, a link exists between inflammation and SDB. Oxidative stress is reflected by UA at baseline and the concentration decreases after treatment according to improvements in SDB.     

Ecology of some species of catfishSynodontis (Pisces: Mochocidae) in the Kpong Headpond in Ghana

Synopsis Some aspects of the ecology of the freshwater catfishSynodontis (Pisces: Mochocidae) in Kpong Headpond (Ghana) were studied. Five species were encountered, namelySynodontis schall, S. gambiensis, S. ocellifer, S. velifer andS. eupterus. S. ocellifer andS. velifer were not recorded in the area before impoundment and might have entered the headpond as eggs or young from the main Volta Lake. Length: weight relationships for the two most important species can be described by the equations: Log W = - 1.76 + 3.12log L (maleS. schall), Log W = -1.33 + 2.89log L (femaleS. schall) and Log W = - 0.39 + 2.07log L (S. gambiensis, sexes combined).Synodontis is omnivorous and generally browses on benthic deposits. Adults feed mostly on chironomids, plant material and aquatic insects. The genus displays sexual dimorphism by having a short urino-genital papilla in most adult males. ForS. schall, one season of major spawning activity occurs per year from mid to late September with first time spawners between 20.0–30.0 cm SL. TheSynodontis species studied lay between 2000 to 209000 eggs per spawning season.     

Length–weight and length–length relationships,gonadosomatic indices and size at first maturity of Eugerres mexicanus (Steindachner, 1863) (Percoidei: Gerreidae) from the Usumacinta River,Mexico

This study examines the length‐weight (L‐W) and length‐length (L‐L) relationships, gonadosomatic indices, and size at sexual maturity for individuals of the endemic Mexican mojarra, Eugerres mexicanus (Steindachner, 1863) from the Usumacinta River Basin, Tabasco, Mexico. From April 2008 to January 2010, 360 specimens were examined, including 151 (41.9%) male, 179 (49.7%) female and 30 unsexed (8.3%) individuals. Overall female:male ratio was 1.2 : 1. Gonadosomatic index (GSI) values indicate increased reproductive activity during February, with significant differences between males (GSI = 2.07) and females (GSI = 5.48). The mean size at first maturity (L₅₀) was 17.3 cm TL for males and 20.5 cm TL for females.     

铜锈环稜螺繁殖和生长的初步研究

作者于1963年3月至1964年6月间对武昌东湖的铜锈环稜螺的某些生态学问题进行了初步研究:自然种群中铜锈环稜螺的性比为1∶1。成熟雌螺全年怀胚,月平均怀胚数以5月初最高,7、8、9月最低,生活于池塘中的雌螺的怀胚数又高于湖泊中相应壳高组雌螺的怀胚数。生殖季节自4月中旬至11月底,其中以6月份产螺达高峰,其临界水温为16—18℃,最适水温在26℃左右。雌螺生长至壳高15—16毫米开始生殖。在自然种群中,每一雌螺每年平均产螺49.7个。雌螺所产仔螺的大小与年龄有关。对铜锈环稜螺的生长规律,提出了有关方程式。       

Rehydration with glycerol: endocrine, cardiovascular, and thermoregulatory responses during exercise in the heat.

The impact of rehydration with glycerol on cardiovascular and thermoregulatory responses during exercise in the heat was studied in eight highly trained male cyclists. Each subject completed three dehydration-rehydration experimental trials that differed only in the rehydration treatment, each separated by 7 days. Before each experimental day, subjects dehydrated to -4% of their body weight by exercise and water restriction. The experimental treatments were as follows: no fluid (NF), glycerol bolus (1 g/kg body wt) followed by water (G), and water alone (W). Rehydration (3% body weight) was given over an 80-min period. After rehydration, subjects cycled (74% peak O2 uptake) to exhaustion in a hot and wet (37 degrees C and 48% relative humidity) environment. For G, plasma volume was expanded (P < 0.05) during rehydration and remained higher than W (P < 0.05) during exercise. Exercise time to exhaustion during G (33 +/- 4 min) was longer (P < 0.05) compared with both W (27 +/- 3 min) and NF (19 +/- 3 min). Cutaneous vascular conductance was significantly elevated (P < 0.05) during G, but G provided no other thermoregulatory or cardiovascular benefits compared with W and NF. Fluid-regulating hormones (vasopressin, aldosterone, atriopeptin, and plasma renin activity) decreased during rehydration and increased during exercise (except atriopeptin), but there were no differences between G and W. These data indicated that glycerol had little or no major effect on fluid-regulating factors during rehydration or exercise, and the improved exercise capacity in G was likely due to a greater plasma volume during exercise.     

Estimation of oxygen-diffusing capacity in the gills of different sizes of a tilapia, Oreochromis niloticus

Measurements on gills of features that affect gas exchange have been studied in relation to body weight in specimens (0.0112–812.3 g) of a tilapia, Oreochromis niloticus . The data were analysed with respect to body weight by means of logarithmic transformations (log Y = log a+b log W ). The slopes ( b ) of the log/log regression lines for the gill area, harmonic mean diffusion distance and oxygen diffusing capacity were 0.777, 0.077 and 0.700, respectively. The gill respiratory area of O. niloticus (Trewavas) increases as the fish develops because the number and bilateral area of secondary lamellae increase. The scaling value for oxygen-diffusing capacity is less than the value for gill area because of the slight increase in harmonic mean diffusion distance with development.     

Length–weight and length–length relationships for some Yangtze River fishes in Tian‐e‐zhou Oxbow,China

Length–weight and length–length relationships are reported for 32 fish species belonging to seven families and 26 genera from the Tian‐e‐zhou Oxbow in the middle reach of Yangtze River, near Shishou City, China. The weight (W) ‐ length (L) relationships were estimated using the logarithmic form of the equation W = aL^b. The exponent b varied from 2.60 to 3.65 (mean ± SE: 3.12 ± 0.25). The 14 weight–length relationships, 13 length–length relationships, and seven maximum lengths are presented to FishBase for the first time.     

Length-weight relationship and condition factor of common minnow, Esomus danricus (Ham.) from different freshwater environments.

Investigations were made on the length-weight relationship and condition factor of Esomu danricus (Ham) from ponds and flowing water channels. These relationships could be represented by the regression equations, log W = -2.6252 + 3.2451 log L (for channel fishes) and log W = -1.5390 + 2.6318 log L (for pond fishes). The correlations were significantly high (P < 0.001). The mean values of condition factors were 0.529 and 0.713 for pond and channel fishes, respectively. The additive action of various factors in stagnant ponds, such as oxygen deficiency, stratification of indispensahle nutrients at the bottom, accumulation of body wastes of fishes, and unoxidized chemical compounds, competition for many necessities of life as space, food, shelter, seemed to adversely affect the growth rate and condition factor of pond dwelling fishes. Contrary to this the circulation of water induced by currents in the channels appeared to cause mixing of water at all depths to even out differences in dissolved oxygen concentration, temperature, nutrients, besides minimizing the effect of repressive factor. Such conditions invariably offered more opportunities to fishes to conserve almost all the available space and other resources in the habitat. This ensured rapid growth as evidenced by higher condition factor of the flowing-water fishes as compared to their counterparts occurring in ponds.     

Effect of starvation and re‐feeding on growth performance and content of plasma lipids,glucose and insulin in cultured juvenile Persian sturgeon (Acipenser persicus Borodin, 1897)

The effect of starvation and subsequent re‐feeding to satiation on compensatory growth performance, insulin and blood serum values were investigated in juvenile Persian sturgeon (Acipencer persicus) with an average weight 108.04 ± 0.28 g (mean ± SEM) and in the same rearing condition over an 8‐week period. Sturgeons were allocated to one of five feeding treatments: controls (C, continuous feeding), W1 (1 week starvation), W2 (2 weeks starvation), W3 (3 weeks starvation) and W4 (4 weeks starvation), followed by a single 4 weeks of re‐feeding to satiation. Changes in growth performance and blood serum indices were examined at the end of weeks 4 and 8. Body weight, specific growth rate (SGR), condition factor (CF) and weight gain were determined to have significantly decreased during starvation. Fish starved for 1 week reached the same weight as the control fish after re‐feeding for 4 weeks, indicating that complete compensatory growth occurred. Although the specific growth rate in W2, W3 and W4 fish was greater than that in the control fish after re‐feeding, W2, W3 and W4 fish did not reach the same body weight as control fish at the end of re‐feeding period, and showed partial compensation only. Blood plasma, glucose and insulin concentrations did not change significantly during starvation and re‐feeding (P > 0.05). This suggests that sturgeon are able to maintain glycaemia during starvation, probably due to their non‐carbohydrate dietary source. Plasma total lipid and triglyceride levels increased in starvation treatments, whereas the increases were significant only in W3 treatment (P < 0.05). After a 4‐week re‐feeding period, their levels decreased in comparison to the starvation periods. Increases in plasma total lipid and triglyceride levels appear to be due to their roles as preferred nutrients for mobilization in Persian sturgeon and the magnitude and duration of compensatory growth depended on the length of food deprivation.