Mackerel (Scomber australasicus) Reproduction in Northeastern Taiwan

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

Blue Cod, Parapercis Colias, Maturity, Fecundity, Sex Change, and Potential Drivers of Sex Ratio in The Marlborough Sounds

<p>Blue cod, Parapercis colias (Pinguipedidae), are widely considered to be the most important recreational finfish species in the South Island. However, blue cod have been declining in abundance in the Marlborough Sounds for many years, and currently, sex ratios are highly male- biased. Blue cod are believed to be a socially structured hermaphroditic species whose populations are prone to local depletion. A potting survey in the Marlborough Sounds was carried out by NIWA in 2013, and along with environmental measurements, 3247 blue cod were measured, weighed, sexed, and stage of sexual maturity was classified macroscopically at sea. Gonads from a subsample of these fish were removed and preserved. In Chapter Two, the preserved gonads were processed histologically and a species-specific histological maturity key was developed. Histological and macroscopic maturity classifications and length-at-maturity estimates were compared. Additionally, estimates of spawning frequency and batch fecundity were made using histological and gravimetric methods. In Chapter Three, possible drivers of sex ratio were investigated using the survey data. Density, large male influence, and environmental factors were considered. In Chapter Four, the feasibility of using digital imaging software to age blue cod otoliths was investigated using the OtolithM application in ImagePro Premier. There was poor agreement between macroscopic and histological maturity classifications (20%, overall). Macroscopic methods overestimated the proportion of mature fish at length in the larger sample, which led to biased length-at-50% maturity (L₅₀) estimates. Macroscopic L₅₀ estimates differed markedly from histology estimates. Using histological data, male L₅₀ was 26 cm TL. Histology indicated that there was no length at which 100% of females were mature. Therefore, a three-parameter capped logistic model was used. Histologically, female L₅₀ was 23.6 cm TL, and the Cap was 0.78, indicating the proportion of mature females reached an asymptote at 0.78. Spawning frequency was 4.6 days, and mean relative batch fecundity was 6.5 hydrated oocytes per gram body weight (SD = 3.3). Hermaphroditism was confirmed for blue cod and was macroscopically identifiable. The analyses in Chapter Three indicated that density had some effect on sex ratio, and large males influenced local sex ratios. Finally, the imaging software could not accurately estimate age compared to an expert reader, and it produced highly variable age estimates. This research found that the macroscopic maturity classifications for blue cod were inaccurate, and revision of the macroscopic key is suggested. The biased estimates of L₅₀ from macroscopic data could lead to biased estimates of spawning stock biomass (SSB). Batch fecundity was markedly lower than the previously reported estimates. The finding of a macroscopically identifiable hermaphroditic stage suggested that ‘hermaphrodite’ should be added as a sex class in the macroscopic key. From the GLM in Chapter Three, in more dense populations, the proportion of males increased. This may have been from changes to male mating strategies, or density may influence the occurrence of primary and secondary males. Finally, areas with males > 45 cm TL had a higher proportion of females, suggesting that large males should be protected in order to help balance sex ratios.</p>

Blue Cod, Parapercis Colias, Maturity, Fecundity, Sex Change, and Potential Drivers of Sex Ratio in The Marlborough Sounds

<p>Blue cod, Parapercis colias (Pinguipedidae), are widely considered to be the most important recreational finfish species in the South Island. However, blue cod have been declining in abundance in the Marlborough Sounds for many years, and currently, sex ratios are highly male- biased. Blue cod are believed to be a socially structured hermaphroditic species whose populations are prone to local depletion. A potting survey in the Marlborough Sounds was carried out by NIWA in 2013, and along with environmental measurements, 3247 blue cod were measured, weighed, sexed, and stage of sexual maturity was classified macroscopically at sea. Gonads from a subsample of these fish were removed and preserved. In Chapter Two, the preserved gonads were processed histologically and a species-specific histological maturity key was developed. Histological and macroscopic maturity classifications and length-at-maturity estimates were compared. Additionally, estimates of spawning frequency and batch fecundity were made using histological and gravimetric methods. In Chapter Three, possible drivers of sex ratio were investigated using the survey data. Density, large male influence, and environmental factors were considered. In Chapter Four, the feasibility of using digital imaging software to age blue cod otoliths was investigated using the OtolithM application in ImagePro Premier. There was poor agreement between macroscopic and histological maturity classifications (20%, overall). Macroscopic methods overestimated the proportion of mature fish at length in the larger sample, which led to biased length-at-50% maturity (L₅₀) estimates. Macroscopic L₅₀ estimates differed markedly from histology estimates. Using histological data, male L₅₀ was 26 cm TL. Histology indicated that there was no length at which 100% of females were mature. Therefore, a three-parameter capped logistic model was used. Histologically, female L₅₀ was 23.6 cm TL, and the Cap was 0.78, indicating the proportion of mature females reached an asymptote at 0.78. Spawning frequency was 4.6 days, and mean relative batch fecundity was 6.5 hydrated oocytes per gram body weight (SD = 3.3). Hermaphroditism was confirmed for blue cod and was macroscopically identifiable. The analyses in Chapter Three indicated that density had some effect on sex ratio, and large males influenced local sex ratios. Finally, the imaging software could not accurately estimate age compared to an expert reader, and it produced highly variable age estimates. This research found that the macroscopic maturity classifications for blue cod were inaccurate, and revision of the macroscopic key is suggested. The biased estimates of L₅₀ from macroscopic data could lead to biased estimates of spawning stock biomass (SSB). Batch fecundity was markedly lower than the previously reported estimates. The finding of a macroscopically identifiable hermaphroditic stage suggested that ‘hermaphrodite’ should be added as a sex class in the macroscopic key. From the GLM in Chapter Three, in more dense populations, the proportion of males increased. This may have been from changes to male mating strategies, or density may influence the occurrence of primary and secondary males. Finally, areas with males > 45 cm TL had a higher proportion of females, suggesting that large males should be protected in order to help balance sex ratios.</p>

Maintenance and spawning on yellowfin tuna broodstock reared in floating net cage

Yellowfin tuna (Thunnus albacares) is one of the fish species that have important economic value which is expected to become one of foreign exchange that can give solution to national economy. Hatchery technology of yellowfin tuna performed at the Research Institute for Mariculture and Fisheries Extension Gondol has been successfully spawned. However, the quality and quantity of eggs produced is still not optimal. The purpose of this study was to determine the performance of spawning on yellowfin tuna broodstock reared in floating net. This research was conducted in cage with a diameter of 48.8 m with a depth of 8 m, filled 90 fishes yellow fin tuna with weights ranging between 50-70 kg per fish. Feed given is: fresh fish, squid and added vitamin C and vitamin E. The study was conducted for 11 months from January to November 2017.The results showed that the yellowfin tuna could spawn monthly. The highest spawning frequency occurred in July at 17 times. The highest total number of eggs harvested was 8,740,350 in October. Hatching rate between 50-92%. Survival activity index (SAI) is 1.8-3.5%. Survival rate of yellow fin tuna during maintenance reached 92.2%.

Reproductive Biology of Carp (Cyprinus carpio) in Batu Bulan Reservoir, Sumbawa, West Nusa Tenggara

Research about carp (Cyprinus carpio) reproductive biology in Batu Bulan Reservoir was conducted in April, May, July, and October 2016. This study aims to determine some biological aspects include the degree of gonad maturity, fecundity, spawning frequency and season, and length of the first gonad maturity. The results showed the sex ratio between male and female fish in April (1:5), May (1:3), July (1:3), and October (1:3), with an average of 1:3.5 with the Chi-Square test on the confidence interval. 95%, it turns out that the sex ratio does not follow the 1:1 pattern, or the sex ratio of the fish is not balanced. TKG II carp occurred every month of observation, while the ripe fish of TKG IV gonads were founded only in April, July, and October. The highest percentage of female fish ripe for TKG IV gonads was 45.32%, and males 67.40% were found in October. The size of the ripening female carp size in Batu Bulan Reservoir is 20.16 cm. Carp fecundity ranges from 1,439 to 40,281.

Effect of dietary astaxanthin on reproductive performance, egg quality and larvae of clowfish Amphiprion ocellaris (Cuvier, 1830)

This study was designed to evaluate the effects of astaxanthin in broodfish diets on reproductive performance, egg quality and larvae quality parameters of clownfish (Amphirion ocellaris). Five treatments were tested with 5 levels of astaxanthin (Carophyll Pink 10% CWS) of 0, 50, 100, 150 and 200 mg/kg added to the feed. Each treatment was repeated in triplicate and the supplemental feeding trials were arranged for 13 months. The results showed that there were significant differences in hatching rate of egg, malformed rate and survival rate of larvae in 3 days post-hatch (p<0.05) among the feeding trials of astaxanthin supplements. The highest hatching rate of egg and survival rate and the lowest malformed rate of larvae were observed in the treatment that was supplemented with astaxanthin 150 mg/kg feed, respectively 92.14 %; 93.57 % and 0.55 %. However, the astaxanthin supplementary diets did not affect the re-maturation and spawning period, spawning frequency, fecundity, egg diameter and larval size of nemo fish among the treatments. The results also suggested that astaxanthin requirement for clownfish broodstock to improve reproductive performance was 150 mg/kg feed.

Maturation Biology and Spawning Ethos of A Hillstream Loach Lepidocephalus Guntea (Ham-Buch) From River Mandal, Pauri Garhwal, Uttarakhand

The paper deals with studies on maturation biology and spawning behaviour of an important hill stream loach Lepidocephalus guntea (Ham-Buch) from river Mandal in District Pauri Garhwal Uttarakhand. It was observed that there was a continuous growth of ova throughout the year. Seven maturity stages in the fish were observed with single mode each month. Gonado-somatic index (GSI) and Dobriyal Index (DI) were calculated to find out the month of peak maturity, spawning frequency and spawning season. It was confirmed by tabulation of fishes in different maturity stages each month and also by physical observations in the field. It was concluded that June was the month of peak maturity and spawning takes place during July- August. Rare spawning was seen even in First week of September. Size at first maturity was 60-61 mm.

Improvement of livebearer fish reproductive performance using Oocyte Developer (OODEV)

Livebearer fish have a unique reproduction by internal fertilization without supplied nutrition from parents. However, increasing the frequency of spawning remains unknown. Therefore, the study aimed to improve reproductive performance by expanding the spawning frequency in three livebearer fish species: guppy, black molly, and platy. Four sets of 10 fish (6 females and 4 males) aged 80 days after birth were maintained in controlled media at 25-28 °C in the separated tank sized 20x20x15 cm. All the fish were fed commercially and mixed with oocyte developer (OODEV) for 14 days at satiation. By using the same fish, spawning and rematuration were observed for 30 and 45 days respectively. The reproductive performance was evaluated for 45 days. The OODEVtreated broodstock showed birthing the larvae in all tanks on the 7th day after treatment, while control fish displayed on the 14th day. The percentage of pregnant broodstock was 66.6-100% in each tank, indicating the OODEV-supplemented diet can be used to increase oocyte growth in the gonad. In the rematuration experiment, the fish spawned a 3-fold increase in frequencies of spawning. These data suggested that OODEV can stimulate oocyte growth and increase the birthing frequency in livebearers.