Total Length Of Males Research Articles

Reproductive dynamics of Peprilus medius captured in the Ecuadorian Pacific

In Ecuador, Peprilus medius is an important fishery resource whose destination is for local consumption and export. There are few local studies on its reproductive biology, and its capture is not regulated. Therefore, this study evaluates the most relevant aspects of its reproductive activity. Samples were obtained monthly from January to December 2017 from the capture of the purse seine fleet and the artisanal gillnet fleet landing near Manta. The morphometric analysis included the length-weight relationship, estimated using the allometry equation. The size at sexual maturity is based on the L50 criterion; the reproductive cycle was determined according to the monthly analyses of the gonadosomatic index (GSI), hepatosomatic index (HSI), and relative condition factor (Kn). A total of 334 specimens were analyzed, with average sizes of 22.0, 21.87, and 21.91 cm of total length (TL), for males, females, and combined sexes, respectively. Sex ratio was 1.17M: 1F (P > 0.05), while the length-weight relationship showed negative allometric growth for both males and females (b = 2.58; CI95% 2.48-2.72). Size at sexual maturity L50 was estimated at 21.84 and 21.23 cm TL for males and females, respectively. The GSI and HSI values and Kn showed significant differences among months (P < 0.05), with a marked seasonality during the single reproductive period. Mean size at first capture of 21 cm TL is recommended.

Reproductive Biology of Ripon Barbel (Labeobarbus Altianalis) In River Kuja-Migori Basin, Kenya

The present study aimed to investigate the reproductive biology of Labeobarbus altianalis from River Kuja-Migori basin, Kenya. This fish species is distributed in most water bodies in the Lake Victoria basin and effluent rivers. Labeobarbus altianalis is susceptible to fishing due to aggregation at the river mouths during reproduction seasons. We conducted a study for 18 months with an objective of determining length at 50% sexual maturity, fecundity, gonadosomatic index, egg size, sex ratio and breeding season of L. altianalis. The results showed that breeding of this fish occurred from March to August and September to November coinciding with longer and shorter rain seasons. Fecundity ranged from 1320-2382 eggs (mean 1552 ± 23.3). There was a strong correlation between fecundity and total length (R2 = 0.994). The mean egg diameter was 1.2 ± 0.007 mm. Mean gonado-somatic index was 5.63 ± 0.34 and 2.24 ± 0.21 for females and males respectively. The length at 50% sexual maturity was estimated to be 16.3 cm and 18 cm total length for males and females respectively. There was no significant difference in sex ratio from the hypothetical 1:1 (χ2, p > 0.05). Females had low fecundity and males attain sexual maturity earlier than females. Results from this study provide important information for managing riverine fishery in the Lake Victoria basin.
 Vol. 9, No. 2, August 2022: 221-228

Length-Weight Relation of the Angular Rough Shark, Oxynotus centrina (Linnaeus, 1758) in the Mediterranean Sea

Oxynotus centrina is considered a rare or uncommon shark species throughout its distribution range. Because of this reason, it is one of the 46 uncommon elasmobranchs in the Mediterranean Sea, which requires filling the knowledge gaps, such as length-weight relations. Based on the analysis of 34 angular rough sharks, the length-weight relations (LWR) of males, females and combined sexes of O. centrina were described as W = 0.216L2.686, W = 0.134L3.041 and W=0.102L3.173, respectively. Total lengths (TL) of females and combined sexes were strongly correlated with total weights (TW); while TL of males was moderately correlated with TW. The b values of LWRs of females and combined sexes (3.041 and 3.173, respectively) were not significantly different from 3.0 (t-test, p>0.10) and indicated positive allometric growth for the examined TL and TW range of O. centrina in the Mediterranean Sea.

Some aspects of the reproductive biology of Labeo victorianus (Boulenger, 1901) from Kuja-Migori River basin, Kenya

Labeo victorianus is an endemic species to Lake Victoria basin and also a species threatened with extinction status. This study investigated reproductive biology of L. victorianus from Kuja- Migori River basin, Kenya with a view to determining the length weight relationship (LWR), condition factor, fecundity, egg diameter gonado-somatic index (GSI), length at 50% maturity (LM50) and sex ratio. Sampling was done by electrofishing from January 2018 to June 2019. The LWR showed a negative allometric pattern (p < 0.05). The mean condition factor for combined sexes was 1.02. Fecundity ranged from 47842 – 101902 eggs (mean ± SD: 83663 ± 2605 eggs) and correlated highly with body size (r2 = 0.9137). Egg diameter ranged from 0.5 – 0.7 mm. Mean GSI was 6.3 ± 1.6 and 2.8 ± 0.45 for females and males respectively. The LM50 was estimated at 18 cm total length (TL) and 20 cm TL for males and females respectively. Sex ratio did not differ from the expected 1:1. This species has a high fecundity with small sized eggs and males attain sexual maturity earlier than females. The findings of this study provide useful information towards sustainable conservation of L. victorianus in the Lake Victoria basin.

Length-weight relationship study of mangrove clam Geloina proxima (Prime-1864) of Dapoli Coast of Ratnagiri District

Mangrove clam Geloina proxima is one of the dominant indigenous bivalves of Ratnagiri Coast. The study of Length-weight relationship of clam G. proxima was carried out during July 2017 to June 2018 to understand growth rate and its pattern. Average total length for males and females recorded was 65.40 mm and 65.25 mm, respectively, which is also supported by the calculation of the weight studies. It is interesting to note that in G. proxima, irrespective of the sex, there is a coordination between the length and weight relationship. In the present study significant difference was observed between the length-weight relationship to weight relationship of male and females of G. proxima. Analysis of results for length-weight relationship in G. proxima indicates negative allometric growth pattern. It is observed that weight of G. proxima bears a curvilinear relationship with the length that becomes linear on logarithmic transformation. The value of correlation coefficient in males was r = 0.97 while the same in females were r =0.98, which were found to be statistically highly significant. The coefficient of determination r2 is an indication of goodness of fit of regression to the observed data. The closer it is to 1, the better is the fit.

New Species of <i>Arrenurus</i> Dugès (Acari: Hydrachnidia: Arrenuridae) from Taiwan

This paper describes a new water mite, Arrenurus wengi sp. nov. from the Guantian Wetland, Tainan City, Taiwan. Male total length (μm) 639, width 528, and height 434, female total length 992, and width 860. Scanning electron microscope images illustrate the structure of male and female species.

Biological and ecological traits of Bathynomus giganteus and Bathynomus miyarei (Crustacea: Isopoda): Contribution to the conservation of deep‐sea in southern Brazil

Abstract This study aimed to determine biological and distributional aspects of deep‐sea giant isopods Bathynomus giganteus and Bathynomus miyarei to assess their extinction risk. Bathynomus giganteus (663 specimens) and B. miyarei (649 specimens) were collected during five research cruises involving 265 h of sampling effort during 32 fishing operations of circular pots, baited traps, ranging from 400 and 1,000 m deep, between 26 and 29°S adjacent to the Brazilian coast. A trend towards larger, sexually mature animals in shallower regions was observed for both species, and depth was the most important environmental variable influencing the animals’ distribution. Bathynomus giganteus were collected between 600 m and 1,000 m depth, while the highest densities of B. miyarei were at shallower depths, between 400 and 600 m. The sex ratio was equal for both B. giganteus and B. miyarei for different seasons, latitudes and bathymetries. The sexual maturity of B. giganteus was estimated at 340–345 mm total length for males and between 280–290 mm for females. Bathynomus miyarei males’ sexual maturity was estimated in the 225–230 mm size class. Bathynomus giganteus showed reproductive activity throughout the year. The longevity of B. giganteus was estimated at 6 years for males and 7.7 years for females. The longevity of B. miyarei was estimated at 9 years for males and 6 years for females. Extinction risk assessment for B. giganteus, which has a greater latitudinal and bathymetric distribution, was evaluated as Least Concern. However, B. miyarei was evaluated in the Data Deficient category.

Fishing gear selectivity on sub-adults and spawning stock of the Tarpon Megalops atlanticus (Actinopterygii: Megalopidae) in Northeast Brazil

The Tarpon (Megalops atlanticus) is a species with economic importance as a food fish and a source of income for artisanal fishers. Research regarding the reproductive biology of this species is scarce or incomplete, especially for this species in northeastern Brazil. Tarpon were caught each month near the Bitupitá district using longline fishing and arrowhead fixed traps, from October 2017 to September 2018. The Tarpon specimens were weighed, measured, and the type of fishing equipment used for the capture was noted. Gonads were obtained and evaluated macroscopically, and fixed and preserved for future microscopic analyses. The present study observed 150 females and 102 males for a total of 252 individuals. The sex ratio was 1:1.5 (M:F) and females showed a dominance in the longer length classes. Both sexes presented negative allometry (b < 3). The gonadosomatic index (GSI), Fulton’s condition (K) values and sexual maturity indicate that the reproductive period occurs between August and November, which is during the dry season. The length at first maturity (L50) presented values of 101.7 cm total length (TL) for females, 99.4 cm TL for males and 101 cm TL for both sexes grouped together. The mean fecundity was 7.5 million oocytes and the species present asynchronous oocyte development, multiple spawning periods, and continuous recruitment of oocytes from the reserve stock indicating indeterminate fecundity.

Reproductive biology of the scalloped hammerhead (Sphyrna lewini) in the central-eastern Pacific Ocean

AbstractThere are limited data regarding the reproductive biology of the scalloped hammerhead (Sphyrna lewini) in Ecuadorian waters, which limits the development of appropriate management measures of its populations. A total of 1664 S. lewini specimens were recorded in Manta, Ecuador in 2003–2009. Specimens were caught by local commercial fisheries and measured between 50–310 cm total length (TL). Females were more frequently caught, with a sex ratio of 1M:1.8F. The median size at maturity was 178.1 cm TL for males and 219.4 cm TL for females, which was larger compared with other localities. Gravid females, which measured 246–298 cm TL, contained 16–22 embryos. Embryos, which were observed from October–July, measured between 11.1–54.6 cm TL and the available data agreed with a gestation period of 10–11 months that starts in September and ends in June/July. Size at birth was 47–55 cm TL. Sampling data indicated that most fishing activity occurred in nearshore and around seamounts in the central-eastern Pacific Ocean, with much of the landed catch comprising immature individuals. This study documents the reproductive biology of S. lewini in the central-eastern Pacific Ocean and provides additional information to improve management and conservation measures for this species.

Reproductive parameters of the shovelnose guitarfish Pseudobatos productus (Ayres, 1856) in Northwest Mexico

The shovelnose guitarfish Pseudobatos productus is a major species in batoid catch on the north-western coasts of Mexico. Our goal was to describe the reproductive biology of this species, including morphometric and histological analysis of the gonads. Sampling was carried out on artisanal fishing camps near Bahía Tortugas, Baja California Sur, Mexico. A total of 147 organisms were collected, with a size of 58.9 to 162 cm of total length (TL). The size of first maturity (L50%) was 111.3 cm TL for females, and 102.2 cm TL for males. The sex ratio was 1.42 females per male, but 1:1 for embryos. Positive correlations were found between TL and the number of oocytes, the diameter of oocytes, the uterus height, the oviducal gland height, the oviducal gland width, and the clasper length. We describe four histological zones in the oviducal gland of females, with no sperm storage. Mature testicle lobes showed distinct spermatogenesis stages, ranging from spermatogonia to mature sperm cells.

Male-biased sexual size dimorphism in sharks: the narrowmouth catshark Schroederichthys bivius as case study

In shark populations, variation in sexual size dimorphism (SSD) appears to be related with the reproductive mode. Here, we aimed to investigate the reproductive biology of the narrowmouth catshark Schroederichthys bivius, an oviparous shark with size and secondary sexual dimorphism. For this purpose, specimens were collected during research surveys covering almost their entire distribution in the southwestern Atlantic continental shelf. Size distribution ranged from 196 to 810 mm total length (TL) in males and from 258 to 630 mm TL in females, and the mean size at maturity was 563 mm TL for males and 485 mm TL for females. Males appeared to be capable of mating all times of the year, while females could exhibit an annual reproductive cycle. Besides SSD, with males attaining higher maximum TL and size at maturity, spatial sexual segregation appears to be observed in mature specimens. Although differences in size at maturity were observed between surveys, these differences did not show a latitudinal pattern. The spatial overlap observed between closed areas to trawling and the distribution of egg-bearing females suggests that these closed areas, although designed and established to protect other species, may represent an important measure also for the conservation of S. bivius.

Effects of salinity on sexual maturity and reproduction of Poecilia velifera

Poecilia velifera is a popular fish in freshwater aquarism that naturally inhabits aquatic habitats with a wide range of salinities. Nonetheless, the effects of different salinities on the reproductive success and sex ratio of the species remain unknown. Male sex characters, sex ratio and reproductive success of P. velifera were evaluated by maintaining 160 juveniles (0.078 ± 0.011 g) in four different salinities (0; 12; 24; 36 g/L), with four replicates. The only modification observed in males was the formation of a copulatory organ from the anal fin, which was used to distinguish them from females. Timing of the formation of the male copulatory organ, and the weight and total length of males when it occurred, were recorded. Twenty-eight fish from each treatment were euthanized after 150 day to examine the gonads and confirm sex. Eight females and four males from each treatment were then kept in their respective salinity treatments for 65 days to examine the effects of salinity on reproduction. Males were kept with females in the different treatments for 15 days, at which point they were removed. Salinity was negatively correlated with male weight and length. Salinity also affected the sex ratio, with the percentages of males and females being 32.5 and 67.5%, and 27.5 and 72.5% in the salinities of 24 and 36 g of salt/L, respectively. Fifty percent of the females kept in freshwater reproduced, while there was no reproduction in the other treatments. The maintenance of P. velifera in freshwater promoted greater reproductive success and precocity, as well as larger males.

Size distribution and sex ratio of scalloped hammerhead shark (Sphyrna lewini) in Banda Aceh fisheries

Scalloped hammerhead sharks (Sphyrna lewini) are top predators in the marine ecosystem. This species also began to be listed in Appendix II CITES in 2013 and received Indonesia government regulation through banning export. Kutaraja is one of fishing port Banda Aceh, and hammerhead sharks often caught as by-catch from coastal and pelagic fisheries that operate in Indian ocean western part of Aceh. This research aims to determine the size distribution and sex ratio of scalloped hammerhead sharks that landed in Kutaraja fishing port. Data were collected including length distribution and sex composition of captured scalloped hammerhead shark during January-December 2017. Results show that the size distribution of hammerhead sharks are between 62 and 272 cm in Total Length (TL) with an average of 131 cm TL for males and between 58 and 281 cm TL with an average of 128 cm TL for females. There was a positive relationship between the total length and clasper length. The Sex ratio of male and female is 1:1.7. The result of this study hopefully will help management effort for this endangered species, especially in how to reduce the by-catch of female and immature hammerhead sharks that dominate the catch in Banda Aceh fisheries.

Aspects of the reproductive biology of the blue shark Prionace glauca (Linnaeus, 1758) in the coastal waters of Ivory Coast, West Africa

AbstractThe blue shark Prionace glauca is the most abundant species in the artisanal driftnet fishery off the coastal waters of Ivory Coast. The reproductive parameters were investigated with the aim of providing basic information on the reproductive biology for fisheries management. A total of 424 specimens (256 males and 168 females) ranging from 170–330 cm in total length (TL) were sampled between August 2014 and November 2016. Sample for embryonic sex ratio was obtained from 18 litters of 503 individuals (255 males and 248 females). The embryonic sex ratio was not significantly different from 1:1 (χ2 = 0.10, P &amp;gt; 0.05, N = 503). The size at 50% maturity (L50) was 218.1 cm TL for males and 223.3 cm TL for females. The litter size based on the number of embryos varied from 6 to 62, with an average of 30 embryos. Mating started in July whereas ovulation, fertilization and uterine eggs occurred in late October–November. Smallest embryos of 3–5 cm in stretch total length (STL) appeared in uterus from November to January. The embryo size varied widely among months, and well-pigmented embryos were already present in April–May samples, although most of them occurred in August–September, suggesting a gestation period of around 11 months. The absence of neonates in catches, as well as parturition females, does not support a hypothesis that parturition takes place in the Gulf of Guinea.

Age, growth, and maturity of the Indian flathead Platycephalus indicus in the waters around Okinawa-jima Island, Japan

Indian flathead Platycephalus indicus (Platycephalidae) is an important fishery resource in tropical and subtropical waters. However, there have been few studies of its life history which is important for resource management because of taxonomic confusion. Here, we determine the age, growth, maturity, and spawning season of P. indicus from 351 specimens [21.7–76.9 cm total length (TL) for females; 19.6–61.9 cm TL for males] collected between August 2006 and August 2009 around Okinawa-jima Island, in southern Japan. Almost all specimens were caught by artisanal fishery. Age was determined by sectioning otoliths: the oldest specimens were seven years in both sexes. Parameters for von Bertalanffy growth functions were L∞ = 72.6, k = 0.48 and t0 = -0.36 for females, and L∞ = 53.6, k = 0.68 and t0 = -0.38 for males. Mean body size of females was larger than males at a given age, indicating females grow larger than males. The spawning season was estimated to be between January and October. The smallest and youngest mature female was 36.1 cm TL and 1.0 year old, while the smallest and youngest male was 22.9 cm TL and 0.4 years old. Moreover, the smallest mature male individual was smaller than the smallest female. Furthermore, we did not observe hermaphroditic gonads. Therefore, we consider that discrepancy in body size between sexes results from the difference in growth rate rather than sex change.

Temporal variation of sex ratio, growth pattern and physiological status ofEutropiichthys vacha(Schilbeidae) in the Ganges River, NW Bangladesh

ABSTRACTThe present study illustrates the first complete temporal variations of sex ratio (SR), length-frequency distributions (LFDs), growth pattern based on length-weight relation (LWR), length-length relationships (LLRs) and physiological status of Eutropiichthys vacha in the Ganges River, Bangladesh. A total of 1386 specimens (male = 652, female = 734) were collected from the fishers catch during January to December, 2016. For each individual, total length (TL), fork length (FL), standard length (SL) and body weight (BW) were measured using digital slide calipers and electronic balance with 0.01 cm and 0.01 g precision. The overall SR differed statistically from the expected 1:1 ratio, although females were greater in percentage throughout the year, except in April. The TL of males and females ranged from 6.2–19.9 cm and 6.5–20.6 cm, respectively. The overall growth pattern was negative allometric for both sexes, though ANCOVA reveals significant difference in LWRs. All LLRs were highly significant wi...

Reproductive biology of the brown smooth-hound shark, Mustelus henlei (Chondrichthyes: Triakidae), off northwestern Mexico based on macroscopic and histological analyses

The brown smooth-hound shark Mustelus henlei is one of the most abundant species caught by the artisanal elasmobranch fishery off northwestern Mexico. The present study estimates the reproductive parameters for M. henlei using, for the first time, histological analysis and survey data collected from May 2008 to May 2016. Mustelus henlei was reported in the landings from February to November each year (n = 1,469). Total length (TL) varied between 450 and 1,530 mm (average = 753 mm, SD = 111). The sex ratio (male:female) was similar to the 1:1 ratio. Gravid females were caught during April, August, and November. Average fecundity was 9. Length at maturity was 656 mm TL for females and 636 mm TL for males, and length at maternity, estimated for the first time for this species, was 676 mm TL. The first phases of spermatogenesis and oogenesis were identified through histological analysis of gonads from immature individuals. Semen storage was detected in the oviducal gland of females at the terminal zone, whereas in males spermatozeugmata was detected in the seminal vesicles. According to the species reproductive parameters, M. henlei can be categorized as a species of high biological productivity among elasmobranchs and can thus support certain level of fishing pressure off northwestern Mexico if adequate fishing management and regulatory measures are employed. Some of the reproductive parameters that were estimated for this species in the present study were different from those estimated for other stocks from Mexican and United States waters.&#x0D; Key words: reproduction, length at maturity, length at maternity, semen storage, Mustelus henlei.

Biomass determination based on the individual volume of the dominant copepod species in the Western Egyptian Mediterranean Coast

The biomass of five copepod species (Oithona nana, Calocalanus pavo, Nannocalanus minor, Clausocalanus arcuicornis and Paracalanus parvus) that dominate the western part of the Egyptian Mediterranean Coast had been determined using the individual volume. The length-weight relationships and physicochemical influences on the length of species were also investigated. Copepod samples were seasonally collected during the period 2008–2009. All volumes and weights of the randomly selected adult individuals were measured. Ten regression equations confirmed that; the species weights depend on the total lengths of males and females of all species. However, the females of the examined species were always heavier and longer than males. The length and weight of both sexes of all species were higher in winter than in other seasons. Temperature is considered the main factor influencing the sizes of adult copepods. It was also found that the mean length of the examined individuals was inversely proportional to temperature. However, all the investigated organisms had adequate high levels of dissolved oxygen and didn't show any change with pH, salinity and transparency.

Population biology of grey gurnard (Eutrigla gurnardus (L.); Triglidae) in the coastal waters of Northwest Wales

The grey gurnard Eutrigla gurnardus (L.) has been identified by ICES as a potential commercial species in the NE Atlantic with recommendations made to derive information on population biology for stock assessment purposes. However, data on the population biology of this species is limited. In this study, data on the age, growth and maturity of grey gurnard were collected by otter trawling in the coastal waters of northwest Wales and Eastern Anglesey. Total length (TL) of fish sampled ranged between 2.1–33.0 cm (male) and 1.9–36.9 cm (female) with the majority of female (70.8%) fish between 11 and 20 cm TL and male fish (70.5%) between 11 and 18 cm TL. The percentage of fish >20 cm TL was larger for females (30.4%) compared to males (17.6%). Total weight (TW) for female and male grey gurnard in the stratified subsample ranged from 1.9 to 499.9 g for females and 2.1–390.0 g for males, with the majority of female (66.3%) and male (76.1%) fish between 10 and 60 g. TL/TW relations for male and female fish and both sexes combined were: TW = 0.006TL³.⁰⁷, TW = 0.007TL³.⁰³ and TW = 0.007TL³.⁰⁵ respectively. Age structure (based on otolith reading) ranged between 0.5 and 7.5 years old for females and 0.5 to 5.5 years old for male with the majority of female (41.7%) and male (46.0%) fish aged as 1.5 years old. The age structure of female and male grey gurnards was significantly different with the majority of older fish (>2.5 years) being female. The von Bertalanffy growth functions were calculated as Lₜ = 32.4[1 − e⁻⁰.²⁴⁽ᵗ ⁺ ¹.⁴¹⁾] for males, Lₜ = 45.9[1 − e⁻⁰.¹⁶⁽ᵗ ⁺ ¹.³⁷⁾] for females and Lₜ = 44.0[1 − e⁻⁰.¹⁸⁽ᵗ ⁺ ¹.²⁰⁾] for both sexes combined. Instantaneous rates of total mortality were similar for males and females and the combined Z value 1.00 year⁻¹ with the natural mortality rate estimated as 0.33 year⁻¹. The size at 50% maturity (L₅₀) was estimated to be 25.3 cm TL for males, females and for both sexes combined. Age at 50% maturity (A₅₀) was 3.2 years for both males and females. The results of this study provide the first information on the population biology of E. gurnardus in the Irish Sea, the first detailed study in the NE Atlantic since 1985 and helps to address the data gap identified by ICES in knowledge of the population biology of this species.

Age and growth of the banded guitarfish Zapteryx exasperata (Chondrichthyes: Trygonorrhinidae)

The banded guitarfish (Zapteryx exasperata) is the third most abundant ray species in the artisanal elasmobranch fishery of Baja California Sur, Mexico. However, there is no biological information about its age and growth parameters, limiting the application of some quantitative population assessment methods, such as demographic models. The aim of the present study was to estimate, for the first time, age and individual growth of Z. exasperata. Biometric data from 244 individuals and 236 vertebrae were analysed. The largest number of banded guitarfish in fishery landings was observed during April and August, with a female:male sex ratio of 1:1.8. The size range was 56.4–103-cm total length (TL) for females and 51.6–92cm TL for males, with females being significantly larger than males (P&lt;0.05). The periodicity of the vertebral edge suggests that growth band pairs form annually. The estimated age structure was 5–22.6 years for females and 4–19.6 years for males, with significant differences between sexes (P&lt;0.01). The goodness-of-fit of three models was evaluated. For the von Bertalanffy growth model, the parameters were as follows. For females: theoretical maximum length, L∞ = 100.71cm TL; growth coefficient, k = 0.144year–1; and theoretical age at length zero, t0 = –0.39years. For males: L∞ = 89.78cm TL; k = 0.174year–1; and t0 = –0.65years.