This study investigates the growth pattern of 33 fish species caught by gillnets from the Egyptian Mediterranean waters off Alexandria between 2018 and 2020. This is accomplished by studying the ...length-weight relationship (LWR), Fulton’s condition factor (kc), the allometric condition factor (ka), and the relative weight condition factor (kn). The b-values of the length-weight relationship of the studied species varied between 2.1382 and 3.6868 according to the results. Only Dentex macrophthalmus (b = 2.1382), Etrumeus golanii (b = 2.4197), and Trichiurus lepturus (b = 3.6868) exhibited different values than the expected range of 2.5 < b less than 3.5. The 95 % confidence interval (CI) and Bailey’s t-test of b-values were tested. In terms of growth pattern, the results showed 20 fish species with an isometric growth pattern, 10 fish species with negative allometric growth, and only 3 fish species with positive allometric growth. The study of Fulton’s condition factor (kc) assessed the differences between species to the differences in fish shape, and proposed that each fish family has its own range depending on the fish shape, and (kc > 1) is not necessarily a better condition for the fish. The study of the allometric condition factor (ka) assessed that the difference between ka and kc values influenced by the feeding intensity and the b-value. The values of the relative weight condition factor (kn) were within the range from 0.929 to 1.038, and 24 fish species reflected a good growth condition while the kn values for the remaining 9 species were less than 1.0. The obtained results add new data about specific species and provide updated data on the remaining species in the area of study. The obtained results can have useful effects on the stock assessment of fish species.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Multiple species of mud crabs are known to co-exist sympatrically within the same ecosystem. However, little is known about the potential factors influencing their community composition. In addition, ...four types of presumed hybrids (SH 1–4) of the genus Scylla with distinct variations in morphological and morphometric characters were reported recently at Kota Marudu Mangrove Forest, Sabah, Malaysia. Therefore, this study described the species composition and investigated the potential species composition-regulating factors of mud crabs in Kota Marudu Mangrove Forest, Sabah, Malaysia. Further, the size distribution, length-weight relationships, and Fulton's condition factors (Ks) of Scylla species, including S. olivacea, S. tranquebarica, S. paramamosain and presumed hybrid SH 1 were also estimated and compared. Interchanging distribution patterns were observed between the two dominating species – S. paramamosain and S. tranquebarica. Interestingly, all four presumed hybrids were only found in September and October 2012. Poisson regression showed that species, sex, and sampling period were influencing factors of Scylla's composition variation. In terms of size, S. tranquebarica was the heaviest and the largest amongst other species. Based on their length-weight relationships, females exhibited negative allometry whereas males showed positive allometry, except S. olivacea males due to their low sampling size. The K values were similar among species and sexes, except S. tranquebarica females with significantly lower mean K values. The results of this study contribute towards the understanding of the relationship between sympatric Scylla species and provide a basis for future hybrid confirmation studies. The description of length-weight relationships and K values of each Scylla species and group serves as essential baseline data for future fisheries management.
•All presumed hybrids (SH 1–4) occurred together during September and October.•Species, sex and month influenced Scylla's composition variation.•S. tranquebarica is the heaviest and the largest.•In all species analysed, males showed positive whereas females showed negative growth allometries.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Schizothorax esocinus, a nutrient-rich food fish offered in Asian countries, is rapidly declining due to severe fishing pressure and pollution in its wild environment, requiring active conservation ...strategies. Our study examined 196 specimens to elucidate critical biological parameters including sex ratio, length-weight relationships (LWRs), Fulton's condition factor (K) and morphometric-meristic parameters. The general sex ratio was not substantially departed from the predicted value of 1 : 1, with the exception for the month of May, where χ2 = 4.15 which is greater than the calculated value of 3.84. The correlation between the length and weight was reported as Log W = 0.134209 + 2.5218 log L for males, Log W = 0.19173 + 2.6751 log L for females and Log W = 0.162116 + 2.594 for combined sexes. Schizothorax esocinus demonstrated a negative allometric growth as indicated by the allometric parameter b for the LWR. The two sexes showed no significant differences in morphometric measures. So, this study included combined-sex regression analysis. These comprehensive findings highlight the critical need for conservation efforts in India and neighbouring countries to preserve this valuable fish stock for future generations.
Slimy sculpin (Cottus cognatus) are increasingly being used as indicator species. This has primarily entailed measuring their condition, the assumption being that condition can be used as a surrogate ...for lipid content. While there is evidence to suggest this assumption is applicable to some fish, it has yet to be validated for C. cognatus. Further, there are several means by which one may calculate condition, the most commonly employed of which are indirect measurements of lipid content (namely, Fulton’s K, somatic K (Ks), and Le Cren’s relative condition factor (Kn)). We compared the ability of each of these morphometric indices to predict whole-body lipid content in C. cognatus. There was a moderate degree of evidence that Fulton’s K, Ks, and Kn are reliable predictors (Ks and Kn in particular). Of the latter we recommend Kn be used because, unlike Ks, it does not require that fish be killed. And while Fulton’s K did not perform quite as well, we consider it a sufficient substitute if the data necessary to calculate Kn are unavailable.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The reproductive success of uniparental males depends much on their nutritional stage (i.e. body condition). Therefore, secondary sexual traits should convey information not only on fecundity but ...also on nutritional stage. To test this hypothesis, we evaluate relationships between head crest height (HCH), as a secondary sexual trait, relative testes mass (an indicator of sperm production), body condition (an indicator of nutritional status) and body mass of males of uniparental Amur sleeper Perccottus glenii in two contrasting habitats. Furthermore, we examined whether head crest is only a pure investment to advertise male fitness – either to females, rival males or other fish approaching the nest – or it comprises some regainable energy as well. We found that HCH is closely related to relative testes mass, and body condition especially at the beginning of the reproductive period. The head crest consisted of a swollen connective tissue in the supraorbital region of the head, and an oedematous epaxial muscle in the nuchal region. Furthermore, the head crest also comprised of adipose tissue, although not as much as assumed. Therefore, we argue that HCH represents a reliable signal of multiple aspects of male quality; it indicates readiness to spawn and could potentially effectively facilitate female choice towards large males with high fecundity and great nutritional stage, which is essential to good guarding performance. Moreover, the head crest itself also could contribute to nest‐guarding performance by virtually enlarging body size and by representing a minor fat reserve.
Secondary sexual traits are often costly and risky advertisers of some aspects of individual fitness, but it is usually not evident what individual traits are actually advertised and how the other sex benefits. Here, we present an empirical example from fishes of a valid relationship between the development of head crest and individual fecundity and body condition in the males of a uniparental species, and show how this could benefit the females.
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BFBNIB, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
This study was conducted to determine length-weight relationship (LWR), condition factor (K), and relative condition factor (Kn) of white bream Blicca bjoerkna (Linnaeus, 1758), inhabiting the Kyiv ...Reservoir (Upper Dnieper, Ukraine). Fishes aged 0+ to 19+ were analysed. Length-weight relationships were found to be W = 0.0439 x SL2.8442 (R2 = 0.9845), W = 0.0320 x SL2.9284 (R2 = 0.9736) and W = 0.0332 x SL2.9267 (R2 = 0.9794) for females, males and combined sexes, respectively. A negative allometric growth (b < 3) was observed for all samples. Calculation of average K resulted as 2.74±0.11 for females, 2.60±0.11 for males and 2.68±0.12 for all specimens. Average Kn of these groups were found to be 1.03±0.04, 0.97±0.04 and 1.00±0.04, respectively. This study is the first reference on LWR equation parameters and Kn of B. bjoerkna in the Dnieper River.
Round goby Neogobius melanostomus were examined from the Bass Islands area in the western basin of Lake Erie, U.S.A., to determine age and growth correlations. A total of 188 specimens were collected ...and examined during summer 2011 with 90 aged using scale analysis. Fish were grouped by sex, depth of habitat and habitat type (anthropogenically modified shallows, natural shallows and open lake deep water). Fish ranged from 17 to 117 mm total length (LT) and 0+ to 3+ years. Males dominated the population (1·94:1) and backcalculated age showed that both sexes grew exponentially, with male growth rate increasing faster than female. Males were significantly larger than females in LT and mass (both P < 0·001). The relative mass index (Wr) was low for the sampled population (mean ± s.d. = 32·00 ± 26·87 g), implying that the health of the Bass Island area population is very poor when compared with the species throughout its range. This could be due to a lack of food resources related to population size or that the fish is not optimally utilizing the available food resources. In contradiction to these findings, regression slope coefficient (b), calculated using Fulton's condition factor (K) (mean ± s.d. =1·50 ± 0·20), was very low for each habitat, implying a healthy population throughout. This seemingly opposite effect may be due to more individuals per unit area in shallow waters, which would cause increased competition for resources. Poor condition may indicate that the Lake Erie population has reached saturation or may reflect indirect fitness costs associated with increasing anoxic or hypoxic hypolimnion conditions.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Rivers in tropical Australia are largely pristine, and ecosystem connectivity is intact, but water resources in northern Australia are under increasing development pressure. A better understanding of ...the role and life histories of key migratory species is urgently needed to manage the risks posed by development. We investigated the life history of Macrobrachium spinipes (Schenkel, 1902) in the Daly River of the Northern Territory, Australia. We carried out a 13-mo trapping program (2011–2012) at 7 sites along the river between 92 and 405 km from the estuary. We provide the first detailed account of spatial and temporal changes in relative abundance and reproduction, and present information on length at first maturity and Fulton’s body condition factor. Reproduction was strongly seasonal and was restricted to the wet-season months of November to April, followed by a recruitment pulse 3 to 4 mo later during the early dry season. Length at first maturity declined as the reproductive season progressed but did not vary significantly with distance from the estuary. Condition was temporally variable and peaked for both sexes immediately after the wet season before declining throughout the dry season. Relative abundance patterns followed a similar pattern. Contrary to results for other Macrobrachium species in rivers of comparable length, we found an increase in the relative abundance of females throughout the river’s length during the reproductive season and reproductive effort occurring far upstream, over a restricted time period. This result highlights the importance of maintaining connectivity for reproductive success of this species and further recruitment into these upstream reaches.
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BFBNIB, IZUM, KILJ, NMLJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
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