This paper describes the weight-length relationships (WLRs) and Fulton's condition factors (K) of skipjack tuna (Katsuwonus pelamis) in purse seine fisheries from three cruises in the western and ...central Pacific Ocean (WCPO): August-September 2009 (AS09), November-December 2012 (ND12), and June-July 2013 (JJ13). The fork length and weight of a total of 1678 specimens were measured. The results showed that the fork length of more than 70% of specimens was below 60 cm (76% in AS09, 87% in ND12, and 73% in JJ13). The coefficient b in the combined sex group was 3.367, 3.300 and 3.234 in JJ13, AS09 and ND12, respectively. The b values of WLRs when fork length was >60 cm were significantly less than 3 (P = 0.062), but when fork length was <60 cm they were significantly greater than 3 (P = 0.028). The K value ranges of JJ13, AS09 and ND12 in different fork length groups were 1.3-1.84 (1.62 ± 0.18), 1.57-2.02 (1.86 ± 0.15), and 1.44-1.78 (0.65 ± 0.13), respectively. Moreover, K values in different fork length classes for each cruise had one turning point: 60-65 cm for JJ13; 60-65 cm for ND12; and 55-60 cm for AS09. The results of this study provide basic information on the WLRs and K values of skipjack tuna in different seasons and growth phases in the WCPO, which are useful for fishery biologists and fishery managers.
This study’s objective was to explore some of the annual Prussian carp’s (Carassius gibelio) biological characteristics (sex ratio, length–weight ratio, and gonado somatic index - GSI) in the Kopački ...Rit Nature Park in Croatia. The Prussian carp is an invasive fish species originated from Asia, which became widely distributed throughout Europe and is believed to be responsible for a decline in the number of indigenous fish, invertebrate, and macrophyte populations in different areas. The fish sampling was conducted from September to November 2017 and from February to July 2018, respectively, using electrofishing. A total of 475 fish individuals were caught and measured for the total length, standard length, body height, and body weight. Males made up 34.31% of the population of Prussian carp. The mean value of Fulton condition factor (FC) of Prussian carp in Kopački Rit was 1.77 ± 0.28. Overall, the FC value had a relatively small amplitude, but it exhibited a clear seasonal vari ability. The average GSI values of females (9.91 ± 5.34) were higher than those of males (3.58 ± 1.37) during the observed period. The average GSI values indicate that the majority of females are spawning in the late April and May, which are also the same periods when other cyprinid species are spawning, allowing the Prussian carp to exploit its gynogenesis strategy.
Cilj ovoga istraživanja bila je istražiti neke od bioloških karakteristika (omjer spolova, dužinsko-maseni odnos i gonadosomatski indeks) babuške (Carassius gibelio) tijekom jedne godine u Parku prirode „Kopački rit“ u Hrvatskoj. Babuška je alohtona vrsta ribe uvezena iz Azije koja se od tada proširila diljem Europe te se vjeruje kako je odgovorna za opadanje autohtone populacije riba, beskralježnjaka i makrofita u pojedinim područjima. Ihtiološko uzorkovanje obavljeno je od rujna do studenoga 2017. te od veljače do srpnja 2018. s pomoću elektroribolova. Ukupno je ulovljeno 475 jedinaka, na kojima je izmjerena ukupna dužina, standardna dužina, visina tijela i masa. Mužjaci su činili 34,31 % populacije babuške. Prosječna vrijednost Fultonova kondicijskog faktora (FC) za babušku u Kopačkome ritu bila je 1,77 ± 0,28. Sveukupno, vrijednosti FC-a su imale relativno malo varijacija, ali ukazuju na jasnu sezonsku varijabilnost. Prosječne vrijednosti gonado-somatskoga indeksa (GSI) za ženke (9,91 ± 5,34) bile su veće negoli za mužjake (3,58 ± 1,37) tijekom promatranoga razdoblja. Prosječne vrijednosti GSI-ja ukazuju kako se većina ženka mrijesti krajem travnja i tijekom svibnja, što je isti period kada se mrijeste i ostale ciprinidne vrste, a to babuški omogućuje da se koristi svojom strategijom ginogeneze.
This work presents new information on the morphological aspects, reproductive biology and diet of the marbled electric ray
Torpedo marmorata
Risso 1810, in the Eastern Ionian and the Aegean Seas, ...from October 2017 to August 2020. The whole dataset consisted of 135 females and 109 males, ranging between 91–464 mm and 99–313 mm in total length (TL), respectively. The weight–length relationship of the species and the length frequency distribution of the sexes were described, corroborating the sexual dimorphism of the species. Thirty-one measurements were recorded to test the allometric growth of several characters for female and male specimens, whereas additional metrics (four) were used to investigate its reproductive cycle, in the north-eastern Mediterranean Sea. Sex ratio analysis was not significantly different from the 1:1 ratio. The size at which 50% of the species attained sexual maturity (L
50
) was the lowest recorded within the Mediterranean Sea for both sexes (261 mm for females and 241 mm for males). Mature males occurred throughout the year, whilst mature females (capable to reproduce) were present in spring and early autumn. The number of embryos ranged from five to 13 per brood. Stomach content examination revealed a preference of
T. marmorata
for fishes, with differences in prey item consumption between the Ionian and the Aegean Sea. This is the first attempt to describe the life-history traits of
T. marmorata
in the Greek Seas that will contribute to the future conservation status of the species.
The present study provides information on weight–length relationship (WLR) and Fulton's condition factor (K) of the alligator pipefish, Syngnathoides biaculeatus (Bloch, 1785) sampled from Palk Bay ...(PB) and Gulf of Mannar (GoM) regions, southeast coast of India. The pooled estimate for the parameter b of the WLR for S. biaculeatus (n = 217) was determined to be 1.75, indicating the negative allometric growth pattern (b < 3). The K values ranged from 0.65 to 1.35 (pooled, 0.84) and from 0.68 to 1.27 (pooled, 0.85) for populations of S. biaculeatus collected from PB (n = 120) and GoM (n = 97) respectively. The results may help address the concerns of conservation of S. biaculeatus in the wake of habitat loss and/or incidental by-catch.
Trachinus draco and Trachinus radiatus are two bycatch species of low commercial value and no sufficient knowledge on their biological features. In the present study, the weight–length relationship, ...age, growth, and ten otolith morphometric variables of these species were investigated in the southwestern Aegean Sea for the first time. Positive allometric and isometric growth in the weight were defined in T. draco and T. radiatus. The weight–length relationship was described by the parameters α = 0.002415 and b = 3.35745 in T. draco and α = 0.007582 and b = 3.09452 in T. radiatus. The von Bertalanffy growth function parameters were L∞ = 44.51 cm, k = 0.15 year−1, and t0 = −1.31 years for T. draco and L∞ = 58.47 cm, k = 0.16 year−1, and t0 = −0.78 years for T. radiatus. Ten otolith variables (radius, length, width, area, perimeter, roundness, circularity, form factor, rectangularity, and ellipticity) showed a significant relationship with size for both species, except the ellipticity in T. radiatus. The mean values of all the otolith variables were higher in T. radiatus than in T. draco. The otolith of T. radiatus was found to become more rectangular with size as compared to the otolith of T. radiatus. The results of this work can support further research on the behavioral and ecological features of the two species.
This study aimed to describe the growth parameters of Anchoa tricolor in a subtropical estuary. From August 2010 to July 2011, 10.009 specimens of the anchovy Anchoa tricolor, mean total length 4.2 ...cm (±1.45), were captured in the intertidal region of the Estuarine Complex of Paranaguá (25º 15' - 25° 35' S and 48° 20' - 48° 45' W). Species´s weight/length relationship for grouped genders was described as follow: W = 0.0000591.Lt3.282 (length in centimeters; weight in grams) showing a positive allometric growth pattern (b>3; P=0.000). Significant differences concerning weight/length relationship for males, females and unsexed individuals were identified. Parameters of the length to age growth curve were estimated by adjusting a von Bertalanffy growth equation from aged individuals from a length-frequency distribution: L∞ = 10.06 (1-e-17715(t + 0.205)) (length in centimeters, age in years). The age to attain 95% of the asymptotic length ( A95 ; longevity sensu Taylor) was estimated at 1.7 years. Size frequency distributions indicate that A. tricolor uses the estuarine area as reproductive and growing grounds, especially during the first year of the life cycle, where the species represent a key element for ecosystem functioning due to relatively high abundance and energy transference from plankton to top predators.
The fecundity and sexual structure of weatherfish (Misgurnus fossilis) population, an inperilled and protected freshwater fish with a poorly known life history, was studied in three waterbodies: the ...River Ner, the Południowy canal and the Nowy Rów canal (Poland) differing in hydrological character. We compared reproductive traits; i.e. sex ratio, absolute and relative fecundity, oocyte size, gonado-somatic index and body condition. In all study sites, the sex ratio of weatherfish did not differ from parity (1: 1), though in the River Ner, the highest GSI values were recorded for females whilst male GSI did not differ among sites. The absolute (FA = 2860 ± 2065) and relative fecundity (FR = 120 ± 55 eggs per g of female body weight) in the River Ner were significantly lower than in the other two sites. In the River Ner the frequency distribution of oocyte diameter, decomposed using the Bhattacharya method, showed two distinct groups in equal numbers. Oocytes that were ready to spawn were larger in the River Ner than in the Południowy and Nowy Rów canals. Fish in the River Ner were also characterized by the lowest Fulton condition index (mean K = 0.36 ± 0.1). The trade-off between impaired fecundity and increased egg diameter may result from the different nature of the studied watercourses or levels of endocrine-disrupting chemicals (EDCs), such as steroid compounds.
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