Search Results (13)

Relatively little is known about size- and age-based reproductive characteristics of Gray Snapper (Lutjanus griseus) despite a large recreational fishery along the west coast of Florida in the Southeastern U.S.A. The purpose of this study was therefore to determine the spawning parameters of Gray Snapper and to quantify female reproductive potential on an age- and size-basis. From 2022 to 2023, 4563 Gray Snapper were collected off the west coast of Florida. Gray Snapper were observed to be actively spawning from late May to early September; however, the percent of females spawning in May and September were both <3%. Batch fecundity for 12 hydrated females showed a hyperallometric relationship with size and age. The spawning fraction also increased disproportionately with female length and age, suggesting older, larger females spawn in greater proportions and more often than younger, smaller females. For females, the length and age at 50% physiological maturity was 292 mm total length (TL) and 2.9 years, and those at 50% functional maturity was 301 mm TL and 3.2 years. Male Gray Snapper reached 50% sexual maturity at 259 mm TL and 1.8 years. The minimum size limit of 10 inches (254 mm) TL in Florida state waters appears to be too low to protect maturing females in particular. These new spawning metrics should be incorporated into future stock assessments to improve estimates of Gray Snapper reproductive output, stock status, and management. Full article

The sterile insect technique (SIT) stands as an eco-friendly approach for mosquito control, but it is impeded by the limited availability of γ-ray radiation source. This research sought to investigate a different radiation source—the Varian Clinac 23EX linear accelerator, which is frequently used for X-ray therapy in cancer treatment. Evaluation parameters including emergence rate, average survival time, induced sterility (IS), male mating competitiveness of irradiated males and fecundity (the number of eggs per female per batch), and the egg hatch rate of females mated with irradiated males were assessed to gauge the application potential of this cancer treatment equipment in the realm of the SIT. The results indicated that X-rays from radiation therapy equipment can effectively suppress the hatch rate of offspring mosquitoes without adversely affecting the emergence rate of irradiated males or the fecundity of females. In addition, at an X-ray dose of 60 Gy, the induced sterility in Ae. aegypti was comparable to the sterility induced by 40 Gy of γ-rays with both treatments resulting in 99.6% sterility. Interestingly, when a release ratio of 7:1 (irradiated males:unirradiated males) was used to competitively mate with females, the IS results resulted by 60 Gy X-rays and 40 Gy γ-rays were still at 70.3% and 73.7%, respectively. In conclusion, the results underscored the potential of the Varian Clinac 23EX linear accelerator as an X-ray source in SIT research. Full article

The fecundity characteristics and spawning strategy of Uroteuthis edulis in the East China Sea were investigated by observing the potential fecundity (PF), relative fecundity by dorsal mantle length (PF_ML) and relative fecundity by body weight (PF_BW). The relationship between fecundity and a single biological indicator was measured, and generalized additive models (GAMs) were fit by adding environmental variables to help better understand this comprehensive relationship. The long diameter and short diameter of the ovarian oocytes ranged from 0.72 mm to 4.74 mm and from 0.46 mm to 3.67 mm, respectively. The long and short diameters of oviducal eggs ranged from 0.61 mm to 5.12 mm and from 0.39 mm to 3.81 mm, respectively. The egg diameter had a unimodal distribution. The PF, PF_ML and PF_BW ranged from 540 to 13,743 cells, 5 to 86 cells/mm and 6 to 53 cells/g, respectively. Three fecundity indicators were unimodally distributed, and the PF_BW was more stable than the PF_ML (δ²PF_BW < δ²PF_ML). The fecundity and single biological indicators were fitted, and it was found that the PF and PF_ML were positively correlated with dorsal mantle length (ML) and body weight (BW). The generalized additive model (GAM) fitting showed that when considering the interaction between dorsal mantle length and sea surface height (M₁₃), the deviation explanation rate of the PF and PF_ML was the highest. Studies have shown that the ovary oocytes of U. edulis mature in batches, and then the eggs are laid in batches. The dorsal mantle length (ML), water temperature at 25 m depth (T₂₅) and sea surface height (SSH) are important indicators to measure the fecundity of U. edulis. These findings allow for a deeper understanding of the U. edulis population dynamics for the future management of this economically and ecologically important species. Full article

Nowadays, overexploitation and climate change are among the major threats to fish production all over the world. In this study, we focused our attention on the Adriatic Sea (AS), a shallow semi-enclosed sub-basin showing the highest exploitation level and warming trend over the last decades within the Mediterranean Sea. We investigated the life history traits and population dynamics of the cold-water species whiting (Merlangius merlangus, Gadidae) 30 years apart, which is one of the main commercial species in the Northern AS. The AS represents its southern limit of distribution, in accordance with the thermal preference of this cold-water species. Fish samples were collected monthly using a commercial bottom trawl within the periods 1990–1991 and 2020–2021. The historical comparison highlighted a recent reduction in large specimens (>25 cm total length, TL), which was not associated with trunked age structures, therefore indicating a decrease in growth performance over a period of 30 years (L_∞90–91 = 29.5 cm TL; L_∞20–21 = 22.8 cm TL). The current size at first sexual maturity was achieved within the first year of life, at around 16 cm TL for males and 17 cm TL for females. In the AS, whiting spawns in batches from December to March, showing a reproductive investment (gonadosomatic index) one order of magnitude higher in females than in males. Potential fecundity (F) ranged from 46,144 to 424,298, with it being heavily dependent on fish size. We hypothesize that the decreased growth performance might be related to a metabolic constraint, possibly related to the increased temperature and its consequences. Moreover, considering the detrimental effects of size reduction on reproductive potential, these findings suggest a potential endangerment situation for the long-term maintenance of whiting and cold-related species in the AS, which should be accounted for in setting management strategies. Full article

Fish with indeterminate fecundity spawn multiple times throughout a protracted reproductive period. During that period several ovulation events succeed one another, and different oocyte developmental stages co-occur in the ovaries with new oocytes consistently recruiting from one growth phase to the next to form the sequential batches. In this study, we examined in detail the oocyte recruitment and development pattern of the sequential batches in a commercially important fish with indeterminate fecundity, the European sardine. The numbers and sizes of oocytes at different developmental stages were estimated for four phases of the ovulatory cycle (ovarian stages) and during the main spawning season (November–March) by applying the oocyte packing density theory in combination with stereological techniques. General linear models (GLMs) were used to test for changes in oocyte sizes as well as relative oocyte numbers per developmental stage within the different ovarian stages in the successive spawning months. A temporal association between several transition events of the oocyte development process was revealed. Specifically, the final maturation of the advanced batch triggered (a) the recruitment of oocytes from primary to secondary growth phase, (b) de novo vitellogenesis and (c) a surge of yolk deposition in primary vitellogenic oocytes. Oocyte recruitment was completed two days after the ovulation of the advanced batch and relative numbers of primary and secondary growth oocytes were thereafter stable until the next final maturation event. This pattern of oocyte recruitment and growth remained unchanged during the course of the spawning season. This study advances our knowledge on oocyte recruitment and development in fish with indeterminate fecundity, which is key to understanding reproduction and its drivers at the individual and population level. Full article

Maurolicus muelleri is a significant component of the marine ecosystem and has the potential to be a valuable fishery resource. However, in the Bay of Biscay, its primary biological traits remain unclear. This study presents data on the length distribution, age, growth, maturity ogive, spawning season, batch fecundity, and sex ratio for Maurolicus muelleri captured in the Bay of Biscay. The results showed that in spring, the adult spawners (ages of 1 and 2) were dominant in the catches, while in September, immature juveniles (age of 0) born in spring were mostly found. Using standard lengths as a basis, 50% of the fish were mature at 34.1 mm (both sexes combined), and the sex ratio, male to female, was 0.44:0.56. The proportion of females increased with length, and a 1:1 sex ratio was predicted at a standard length of 41.5 mm. The spawning season was allocated to at least between March and September, with a likely peak in May. The batch fecundity ranged from 114 to 919 oocytes/female, and increased with the weight and length of females. The results allowed us to interpret a life history strategy for this species, i.e., a high fecundity for females, which mostly participate in one or two reproductive seasons. Therefore, any possible exploitation of age 0 fish prior to spawning could lead to a decrease in the population from which recovery could be slow. Full article

The sub-order Scorpenoidei appears to be particularly interesting due to the presence of intermediate stages between oviparity and viviparity in several species. The present study aims to describe the ovarian morphology, using a histological and histochemical approach, in four ovuliparous species belonging to Scorpaena genus compared with a zygoparous species, H. dactylopterus, focusing also on the assessment of the ovarian dynamics in the populations of such species in Sardinia waters (central–western Mediterranean). Ovarian sections of all species were examined using light microscopy. All species showed a specialized ovary, cystovarian type II-3, strictly related to the production of gelatinous matrices surrounding the eggs. Some microscopic peculiarities in the oogenesis process were found: thin zona pellucida, small and low cortical alveoli, and a specialized ovarian wall during the spawning period. All species analyzed were batch-spawners with an asynchronous ovarian organization. A continuous recruitment of oocytes and the occurrence of de novo vitellogenesis was also observed. During the spawning period, low atresia intensity was detected, while a marked increase in this intensity found in the ovaries at the end of spawning season. Our observations may support an indeterminate fecundity type for these species. Full article

Blue mackerel (Scomber australasicus) is a crucial target species for coastal fisheries in Taiwan, and additionally it has maintained its status as the highest-produced species. The timely measurement of spawning status is crucial for determining the correct management strategy for this species. The objective of this study was to determine size at maturity, fecundity, batch fecundity, and spawning frequency on the basis of samples collected from Nan-Fang-Ao fishing port in Yilan, during the spawning season from 2017 to 2019. Histological sections indicated that the blue mackerel were multiple spawners; a higher percentage of female fish spawned at the peak of the gonadosomatic index. The 50% sizes at maturity were 32.02, 32.13, and 29.64 cm. Mean total fecundity (batch fecundity) was 165 (103), 229 (96), and 210 (68) oocytes per ovary-free weight (g) for 2017, 2018, and 2019, respectively; fecundity was determined through observation of postovulatory follicles (POFs). The spawning frequencies (spawning fraction) in 2017, 2018, and 2019 were 3–10 days (0.13), 4–14 days (0.08), and 4–12 days (0.09), respectively. The spawning frequencies determined through the three estimated methods, namely the sums of (a) hydrated and Day 0 POFs; (b) Day 1+ POFs, and (c) all data combined, were 1 spawning event per 8, 10, and 9 days, respectively. The reproduction of the blue mackerel was greater in 2017 than it was in 2018 or 2019, as indicated by the higher batch fecundity and shorter spawning seasons. Environmental factors should also be considered as a major factor influencing successful reproduction and spawning season Full article

While insect predators need high-quality food to reach sexual maturity and reproduce, starvation following adult eclosion may occur when prey are missing in agroecosystems. This study explores whether the type of diet available at eclosion determines the future fecundity of newly emerged adult predators. In a laboratory experiment, three different diets (i.e., flowers of Perilla frutescens (L.) Britton, eggs of Ephestia kuehniella Zeller as prey, or no food) were offered to adult females of the ladybird beetle Harmonia axyridis Pallas during their first three days after adult eclosion. On the fourth day, each female was paired with a prey-fed male and the pair was subsequently fed with prey. Diet at eclosion did not affect pre-oviposition time, the number of eggs oviposited daily, or the viability of egg batches. High variability in pre-oviposition time among females was observed for all diets. Significant negative linear relationships were found between pre-oviposition time and both the number of eggs oviposited daily and the viability of egg batches. This study clarifies that the food readily available at adult eclosion does not affect the capacity of H. axyridis to reproduce, provided that adults find prey within a few days. More generally, it shows that the reproductive traits of H. axyridis allow this generalist predator to be highly adapted to heterogenous environments in its native range. It is concluded that the variety of habitats offered by diversified agroecosystems may highly benefit the ladybird beetle H. axyridis, and potentially enhance its ability to biologically regulate crop pests. Full article

The study focused on the macroscopic, histological, and biometric analysis of European hake females in GSA 17 (Central-North Adriatic Sea). From 2013 to 2015, 976 females were collected and analyzed monthly. Though females in spawning conditions were found during the whole year, the trend of GSI showed a peak of the reproductive season from April to July in 2014 and 2015. HSI and K_n reached the highest values in September, after the spawning peaks. In 2013, the trend of these indices did not highlight an evident peak, probably due to an adverse event that occurred in the previous winter in the Adriatic shelf. The length at first maturity (L₅₀) was estimated by macroscopic and histological approaches, resulting in 30.81 cm for the macroscopical length and 33.73 cm for the histological length; both values are higher than the current catching legal size. For the first time in this area, batch and relative fecundity were estimated. Relative fecundity was similar to the Mediterranean and the Atlantic stocks, whereas batch fecundity values were lower compared to other fishing grounds. Overall, the analysis of reproductive parameters plays a fundamental role in the sustainable management of this resource in an area as overfished as the Central-North Adriatic Sea. Full article

Background: Zebrafish are efficient animal models for conducting whole organism drug testing and toxicological evaluation of chemicals. They are frequently used for high-throughput screening owing to their high fecundity. Peripheral experimental equipment and analytical software are required for zebrafish screening, which need to be further developed. Machine learning has emerged as a powerful tool for large-scale image analysis and has been applied in zebrafish research as well. However, its use by individual researchers is restricted due to the cost and the procedure of machine learning for specific research purposes. Methods: We developed a simple and easy method for zebrafish image analysis, particularly fluorescent labelled ones, using the free machine learning program Google AutoML. We performed machine learning using vascular- and macrophage-Enhanced Green Fluorescent Protein (EGFP) fishes under normal and abnormal conditions (treated with anti-angiogenesis drugs or by wounding the caudal fin). Then, we tested the system using a new set of zebrafish images. Results: While machine learning can detect abnormalities in the fish in both strains with more than 95% accuracy, the learning procedure needs image pre-processing for the images of the macrophage-EGFP fishes. In addition, we developed a batch uploading software, ZF-ImageR, for Windows (.exe) and MacOS (.app) to enable high-throughput analysis using AutoML. Conclusions: We established a protocol to utilize conventional machine learning platforms for analyzing zebrafish phenotypes, which enables fluorescence-based, phenotype-driven zebrafish screening. Full article

In sub-Saharan Africa, urban populations are projected to increase by 115% in the coming 15 years. In addition, economic growth and dietary shifts towards animal source foods have put high pressure and demand on agricultural production. The high ecological footprint of meat and dairy production, as well as high feed costs, prevent the livestock sector from meeting the increasing demand in a sustainable manner. Insects such as the black soldier fly (BSF) have been identified as potential alternatives to the conventionally used protein sources in livestock feed due to their rich nutrient content and the fact that they can be reared on organic side streams. Substrates derived from organic byproducts are suitable for industrial large-scale production of insect meal. Although efficient in waste management and in feed production, BSF larvae are very sensitive to the external environment such as temperature and rearing medium. Therefore, we studied the effect of temperature and substrate type, i.e., brewers’ spent grain (SG) and cow dung (CD), on the development and survival of BSF larvae. Both organic substrates were readily available in Nairobi, Kenya, the location of the experiments. In our experiment, 100 3–5-day-old BSF larvae were placed into containers that contained either SG or CD and further treated at temperatures of 15 °C, 20 °C, 25 °C, 30 °C, and 35 °C. The duration of larval development was recorded, and the prepupae were removed, weighed, and placed individually in separate, labeled, 35-mL plastic cups filled with moist sawdust. After emergence, 10 2-day-old adults (5 males and 5 females) from every replica per substrate were transferred into a cage (40 × 40 × 40 cm) and allowed to mate for 24 h at their respective temperatures. The laid egg batches were collected and counted, and the adult flies’ longevity was recorded. The data were subjected to a two-way analysis of variance (ANOVA) using the general linear model procedure. BSF larvae reared on SG developed faster than those reared on CD; the former also favored higher temperatures for their larval development and emergence into adults. The optimum range was 25–30 °C. With increasing temperatures, the longevity of adult BSF decreased, while the fecundity of females increased. Thus, it is possible to take advantage of the readily available SG waste streams in the urban environments of Kenya to produce BSF larvae-derived livestock feed within a short duration of time and at relatively high temperatures. Full article

Little is known about the concerted influence of temperature and salinity on the fecundity of clupeid fishes. Due to a globally changing climate, both physical parameters might act as stressors, severely affecting the reproductive potential of clupeid fish populations inhabiting tropical estuaries. Differences in relative batch fecundities, the gonado-somatic index, and the condition index of bonga shad (Ethmalosa fimbriata) were analysed in individual females sampled at the Senegalese coast and inside the inverse Sine Saloum estuary, where salinity increases upstream in all seasons. Multiple linear regression models on fecundity and gonadal energy storage show that clupeids can adapt towards increasing their reproductive investment at temperatures (26–30 °C) and salinities (42–51), which by far exceed marine conditions, in an effort to maximize recruitment success. This reproductive strategy, however, is accompanied by a trade-off between reproductive effort and somatic growth, which ultimately limits the species’ reproductive potential inside the estuary. The observed high variability in batch fecundities might be a viable mechanism to adjust to fluctuating and rather extreme environmental conditions. Understanding the spawning biology of exploited clupeid fishes in drastically changing environments is crucial for evaluating the reproductive potential of stocks at the outer reach of their physiological performance curve. Full article