Fecundity and spawning season of striped mullet (Mugil cephalus L.) in South Carolina estuaries

Fecundity in striped mullet (Mugil cephalus) from South Carolina correlated highly with length and weight, but not with age. Oocyte counts ranged from 4.47 × 105 to 2.52 × 106 in 1998 for fish ranging in size from 331 mm to 600 mm total length, 2.13 × 105to 3.89 × 106in 1999 for fish ranging in size from 332 mm to 588 mm total length, and 3.89 × 105 to 3.01 × 106 in 2000 for fish ranging in size from 325 mm to 592 mm total length. The striped mullet in this study had a high degree of variability in the size-at-age relation-ship; this variability was indicative of varied growth rates and compounded the errors in estimating fecundity at age. The stronger relationship of fecundity to fish size allowed a much better predictive model for potential fecundity in striped mullet. By comparing fecundity with other measures of reproductive activity, such as the gonadosomatic index, histological examination, and the measurement of mean oocyte diameters, we determined that none of these methods by themselves were adequate to determine the extent of reproductive development. Histological examinations and oocyte diameter measurements revealed that fecundity counts could be made once developing oocytes reached 0.400 μm or larger. Striped mullet are isochronal spawners; therefore fecundity estimates for this species are easier to determine because oocytes develop at approximately the same rate upon reaching 400 μm. This uniform development made oocytes that were to be spawned easier to count. When fecundity counts were used in conjunction with histological examination, oocyte diameter measurements, and gonadosomatic index, a more complete measure of reproductive potential and the timing of the spawning season was possible. In addition, it was determined that striped mullet that recruit into South Carolina estuaries spawn from October through April.

Age and growth of the bastard grunt (Pomadasys incisus: Haemulidae) inhabiting the Canarian archipelago, Northwest Africa

The bastard grunt (Pomadasys incisus) is one of the most abundant coastal demersal fishes inhabiting the Canary Islands. Age and growth were studied from samples collected between October 2000 and September 2001. Growth analysis revealed that this species is a fast growing and moderately short-lived species (ages up to seven years recorded). Length-at-age was described by the von Bertalanffy growth model (L∞=309.58 mm; k=0.220/year; t0=–1.865 year), the Schnute growth model (y1=126.66 mm; y2=293.50 mm; a=–0.426; b= 5.963), and the seasonalized von Bertalanffy growth model (L∞=309.93 mm; k=0.218/ year; t0= –1.896 year; C=0.555; ts=0.652). Individuals grow quickly in their first year, attaining approximately 60% of their maximum length; after the first year, their growth rate drops rapidly as energy is probably diverted to reproduction. The parameters of the von Bertalanffy weight growth curve were W∞=788.22 mm; k=0.1567/year; t0= –1.984 year. Fish total length and otolith radius were closely correlated, r2=0.912. A power relationship was estimated between the total length and the otolith radius (a=49.93; ν=0.851). A year’s growth was represented by an opaque and hyaline (translucent) zone—an annulus. Backcalculated lengths were similar to those predicted by the growth models. Growth parameters estimated from the backcalculated sizes at age were L∞=315.23 mm; k=0.217/year; and t0= –1.73 year.

Estimated ages of red porgy (Pagrus pagrus) from fishery-dependent and fishery-independent data and a comparison of growth parameters

The red porgy, Pagrus pagrus, is an important reef fish in several offshore fisheries along the southeastern United States. We examined samples from North Carolina through southeast Florida from recreational (headboat) and commercial (hook and line) fisheries, as well as samples from a fishery-independent source. Red porgy attain a maximum age of at least 18 years and 733 mm total length. The weight-length relationship is represented by the ln-ln transformed equation: W = 8.85 × 10–6(L)3.06, where W = whole weight in grams, and L = total length in mm. The von Bertalanffy growth equation fitted to the most recent, back-calculated lengths from all the samples is Lt = 644(1 – e –0.15(t + 0.76)). Our study revealed a difference in mean length at age of red porgy from the three sources. Red porgy in fishery-independent collections were smaller at age than specimens examined from fishery-dependent sources. The difference in length-at-age may be related to gear selectivity and have important consequences in the assessment of fish stocks.

An evaluation of back-calculation methodology using simulated otolith data

I simulated somatic growth and accompanying otolith growth using an individual-based bioenergetics model in order to examine the performance of several back-calculation methods. Four shapes of otolith radius-total length relations (OR-TL) were simulated. Ten different back-calculation equations, two different regression models of radius length, and two schemes of annulus selection were examined for a total of 20 different methods to estimate size at age from simulated data sets of length and annulus measurements. The accuracy of each of the twenty methods was evaluated by comparing the back-calculated length-at-age and the true length-at-age. The best back-calculation technique was directly related to how well the OR-TL model fitted. When the OR-TL was sigmoid shaped and all annuli were used, employing a least squares linear regression coupled with a log-transformed Lee back-calculation equation (y-intercept corrected) resulted in the least error; when only the last annulus was used, employing a direct proportionality back-calculation equation resulted in the least error. When the OR-TL was linear, employing a functional regression coupled with the Lee back-calculation equation resulted in the least error when all annuli were used, and also when only the last annulus was used. If the OR-TL was exponentially shaped, direct substitution into the fitted quadratic equation resulted in the least error when all annuli were used, and when only the last annulus was used. Finally, an asymptotically shaped OR-TL was best modeled by the individually corrected Weibull cumulative distribution function when all annuli were used, and when only the last annulus was used.

Biology and morphometry study of Drepane punctata (Cuv and Val) at juvenile stage of Bombay coast

The metric and meristic characters of Drepane punctata from Versova Fish Landing Centre of Bombay have been studied. The meristic characters showed considerable variations. The number of dorsal fin rays were relatively stable characters. Statistical interpretation of metric data indicated that there is a direct relationship between the preanal, predorsal in relation to total length and eye-diameter in relation to head length.

Anchorage of air bladder with the interspinous bone of the anal fin in Lactarius lactarius (Bloch and Schneider, 1801)

Specimens of the false trevally (Lactarius lactarius ), 127 to 221 mm in total length, were studied for the mode of anchorage of the air-bladder with the interspinous bone of the anal fin. The 1st and 2nd interspinous bones are fused together into a single piece (named here as the anchor bone) which pierces through the air-bladder, dividing it into two intercommunicating chambers at its upper end, and ultimately articulates with the 10th vertebral bone. The lower end of the bone is broad, fan like with one side affording articulation with the 1st and 2nd anal spines. This is an unique feature of great taxonomical importance to L. lactarius, the only species in the family Lactariidae. The anal fin counts (23-27) and vertebral counts (23) are also given.

Studies on maturity, spawning and fecundity of Nemipterus japonicus (Bloch) off Bombay coast

Studies indicated spawning season of Nemipterus japonicus off Bombay coast (Maharashtra, India), to be during July to December with peak breeding during November to December. Females attained first maturity at the length range 110-120 mm; 50% maturity and spawning occurred at 135 mm within one year of its age. Overall male: female ratio for the entire period of study was 1:1.01. Relationships of fecundity with total length of fish, total ovary weight and per g. fish weight were worked out as F=(-72674.33) L super(739.73); F =65.44 W super(807.33); F=3112.57 W super(22383.27) and F=467.85 W super(4.96) with coefficient of correlation values (r) 0.9090, 0.9443, 0.9911 and 0.8843 respectively.

Karyotypic studies of freshwater prawn Machrobrachium rosenbergii

Chromosomal studies were conducted on Macrobrachium rosenbergii. On the basis of 50 metaphase plate counts, 38 metacentric, 14 sub metacentric and 66 telocentric chromosomes (2n = 118) were observed. The total length of the granomme was recorded to be 34.2 micron.

Reproductive biology of Parapenaeopsis stylifera

Controversy exists regarding the incidence and reproductive habits of Parapenaeopsis stylifera along the coast of Kerala, India. Results are reported of a detailed study on the different aspects of the reproductive biology based on the trawl catches landed at Neendakara Coast for a period of one year. This species breeds throughout the year with peak breeding activity in May and November. The monsoon catches consist of juveniles. Life span of the species is 2.5 years and total length at first maturity is 75 mm. Measures for the effective management of the species in the area are discussed.

Fecundity of the sole Euryglossa orientalis (Bl. & Schn.)(family: Soleidae) from Karachi coast

During the present study fecundity of 30 ovaries of Euryglossa orientalis was determined. Fecundity ranged from 9922 to 8389 with a mean value of 36361. The number of ova in the dorsal lobe was less than that of ventral lobe. Log-log relationship between fecundity and total length, fish weight, ovary weight and ovary length were determined.

Field trials on culture of Clarias batrachus

Culture of Magur, Clarias batrachus on an experimental basis was carried out for a total of 159 days in 6 earthen ponds each of 0.02 ha in area, singly in 2 ponds and in combination with Rohu, Labeo rohita in 4 ponds. Three different artificial feeds were used. Growth of Magur varied from 89 to 110 and survival form 93 to 100%. Out of the 3 feeds used, feed formulation 2 yielded better results. Length-weight relationship parameters were found as log W=0.4979067+1.878346 log L; -1.1116438+2.3511497 log L; and -1.238157+2.433125 log L indicating growth to be not isometric. Relative condition factor (K u) was close to or higher than 1.0 only in fishes higher than 200 mm of total length; K. values which were less than 1.0 up to January, reached values greater than 1.0 by March-April. Condition appears to be influenced by spawning rather than feeding.

Studies on growth and mortality of Cyprinus carpio (Lin.) in floating ponds

Growth and mortality rate of Cyprinus carpio (Linnaeus) under five different dietary conditions were studied in fifteen floating net cages in ponds of the Bangladesh Agricultural University Campus, Mymensingh. Growth rate was found to vary under different dietary conditions. The feed with mixture of 25% rice bran, 5% wheat bran, 30% linseed oil cake and 40% water hyacinth leaf meal exhibited the highest growth rate. The gain of log of body weight per unit increase of log of total length was significant. Significant survivals of the fishes were found.

Culture feasibility of african catfish (Clarias gariepinus Lin.) fry in glass tank and synthetic hapa system using supplemental diets

An experiment was carried out with 1 0 days old Clarias gariepinus fry over a period of 42 days to determine the effects of different feeds on growth and survival of African catfish fry in glass tanks. The experiment was designed into four treatments each having three replications. Thus treatment 1 (T1) was named as Tank Tubifex (TT) and treatment 2 (T2) as Tank Sabinco (TS), treatment 3 as Pond Tubifex (PT), and treatment 4 (T4) as Pond Sabinco (PS). Live Tubifex (protein levels 64.48%) was supplied to treatments 1 and 3 and rest of the treatments were supplied Sabinco starter-1 (protein levels 40.13%). The highest and the lowest growth in total length and weight were 12.90cm, 18.77g and 6.17cm, 4.04g recorded from the treatments 3 and 2, respectively. Growth of catfish fry under treatment 3 in terms of both length and weight were significantly higher (P<0.01) than those of the other treatments. However treatment 2 showed the significantly lowest (P<0.01) growth performance among the various treatments. The highest survival rate (92%) was also obtained with treatment 3. Tubifex proved to be the best larval feed in respect of growth and survival rate.

Rearing of Clarias batrachus (Lin.) larvae with formulated diets

An experiment was carried out for a period of 20 days using 7-day old Clarias batrachus larvae of initial total length of 7.4 ± 0.49 mm and weight of 2.9 ± 0.83 mg. Three artificial diets were used for the study having three replication of each. Among these, diet-I was formulated using 20% fish meal (FM), 30% powdered milk and 30% boiled egg yolk (BEY), diet-II using 27% FM, 20% Baker’s yeast (BY), 30% BEY and 3% agar and diet-III using 20% FM, 20% BY and 45% whole egg. The larvae fed on diets-II and III showed significantly (P<0.05) better length and weight gain than those of the larvae fed on diet-I. The larvae fed on diet- III showed the best survival rate (70%). However, the condition factor of the larvae fed on diet I was significantly better than those of the larvae fed on other two diets. The results of the study showed that C. batrachus larvae could be successfully reared with diet containing 45% whole egg, 20% yeast and 20% fish meal.

Growth and survival of Clarias batrachus (Lin.) larvae fed on formulated diets

An experiment was conducted for a period of 28 days using 7-day old C. batrachus larvae of initial total length (±S.D.) of 7.4 ± 0.49 mm and weight (±S.D.) of 2.8 ± 0.75 mg. Five test diets viz. diets I, II, III, IV and V were prepared. Diet I was formulated using 30% fish meal (FM), 20% soybean meal (SM) and 20% Baker's yeast (BY), diet III using 15% FM, 20% SM, 15% cotton seed meal and 30% BY and diet IV using 20% FM, 30% BY and 30% powdered milk. The remaining two diets (diets II and V) were prepared using minced clam meat (96%) and BY (90%) respectively as the sole source of protein. Three replications were used for each treatment. The larvae fed on diet II exhibited significantly (P<0.05) better length gain and specific growth rate (SGR) than those of the larvae fed on diet III and there was no significant difference among the length gain and SGR of the larvae fed on diet I,II,IV and V. The larvae fed on diet II also showed significantly better weight gain and survival than those of the larvae fed on other diets. There was no significant difference between the condition factor of the larvae fed on diet II and IV. However, the larvae fed on diet II showed better condition factor than those of the larvae fed on other diets.