Gonad Weight Research Articles

ASPECTS OF REPRODUCTIVE BIOLOGY AND ABUNDANCE OF AFRICAN BONYTONGUE (HETEROTIS NILOTICUS) IN GREAT KWA RIVER, NIGERIA

This study was conducted to evaluate some aspects of the reproductive biology of the African Bonytongue Heterotis niloticus from the Great Kwa River, Cross River State Nigeria with the view to encourage conservation and rational measures for sustainable management of the species. A total of 62 matured H. niloticus were sampled and their gonadosomatic index (GSI), hepatosomatic index (HSI), condition factor, fecundity and egg diameter (mm) were studied in other to determine the spawning season of the fish. Gonadosomatic index and hepatosomatic index showed an inverse relationship during spawning seasons. Total length (TL-cm) ranged between 47.1 cm – 76.2 cm and total weight (TW – g) ranged between 4300g - 1169g with sex ratio of 1:1.2 (male: female) revealing a dominant female population. Fecundity ranged from 511 oocytes (48.4cm TL; 1.69 kg wt, 5.9g gonad weight) to 7822 oocytes (69.3cm TL, 3.11kg wt. 14.9g gonad weight). The regression equation derived from the scattered diagram in the relationship between fecundity and total weight, total length gonadosomatic index and length-weight is; F= 6.6231TW0.837, R2= 0.2456; F= 5.1112TL1.6367, R2= 0.1606; F= 10680GSI0.9276, R2= 0.6567; TW= 0.4072TL2.0987, R2= 0.7533, the relationship were significant (p < 0.05). Fecundity and ovary weight relationship showed a positive correlation coefficient of 1. The highest egg diameter (0.92±0.01) was recorded in May and other months with corresponding high gonadosomatic index performance to confirm spawning period. In view to encourage conservation by investigating measures for sustainable management of the species, this study observed that H. niloticus spawns throughout the year.
 Ikot, N. U. | Department of Zoology and Environmental Biology, University of Calabar, P.M.B.1115 Calabar, Nigeria

Fecundity of Atlantic sturgeon ( Acipenser oxyrinchus Mitchill, 1815) captured by the commercial fishery in the Saint John River, New Brunswick, Canada

Knowledge of fecundity in fishes is important for understanding life history, modeling population dynamics, developing fisheries management and determining conservation status. Sturgeon species are known for their high fecundity but to date only two populations of Atlantic sturgeon (Acipenser oxyrinchus Mitchill, 1815) have been examined for this aspect of their biology. The species is protected in most regions of eastern North America but the Saint John River, New Brunswick supports one of the two remaining commercial fisheries in Canada. Sixty females selected by this fishery were sampled for total length, weight, age, gonad weight and egg number. Absolute fecundity ranged from 153,630 to 1,306,626 eggs, with a mean fecundity of 582,832 ± 261,806 eggs. Absolute fecundity exhibited a significant positive relationship to increasing body weight but not to total length or age. Relative fecundity ranged from 129 to 216 eggs/g gonad weight and although it declined with both increasing body size and age the relationships were not significant. The Gonadosomatic Index (GSI) ranged from 1.3% to 27.0% with a mean of 7.8% ± 4.94 SD. Relative fecundity found in this study was higher and mean GSI lower than reported for other Atlantic sturgeon populations and other sturgeon species. Differences were probably due to location of the fishery downstream from spawning sites and selection of pre-spawning females by the commercial fishery.

Effect of melatonin on gonad and thyroid development of offspring of hypothyroid pregnant rats

ABSTRACT We investigated the effects of melatonin on rats with induced hypothyroidism during gestation as well as its effect on the development of the gonads of their offspring. Fifteen pregnant rats were divided into three groups: GC, rats without induced hypothyroidism; GH, rats with induced hypothyroidism; GHM, rats with induced hypothyroidism plus melatonin. Hypothyroidism was induced by oral administration of 6-propyl-2-thiouracil and melatonin was applied subcutaneously. Treatments were performed during gestation and lactation. For the matrices, we evaluated the number of pups, body weight gain, ovarian weight, thyroid weight, organosomatic index, thyroid stimulating hormone (TSH) dose and thyroid morphometry. For the pups, weight gain, TSH, weight, morphometry of the gonads and organosomatic index were analyzed, as well as the cell proliferation index. TSH was elevated only in the matrices of GH animals. Melatonin prevented reduction of ovarian and thyroid weight, number of pups, follicular diameter and thyroid epithelial proportion of the matrices with hypothyroidism. The offspring of rats of the GH group exhibited less body weight gain, gonad and thyroid weight, and gonad cell proliferation index compared to the offspring born of rats of the GC and GHM groups. Melatonin prevented the effects of maternal hypothyroidism on the offspring of rats.

Reduced biomass of the kelp Saccharina japonica cumulatively affects gonad production of sea urchins over ensuing years off northeastern Japan

The annual kelp Saccharina japonica grows along the northeastern coast of Japan, making the coast highly productive for the fishery for herbivores such as sea urchins and abalones. The biomass of the kelp along this coast drastically varies each year due to variable environmental factors, i.e., seawater temperature and nutrient concentrations, during the period of kelp germination. We carried out a field investigation to elucidate how the gonad production fluctuates in an environment where the kelp production varies each year. Seaweed biomass and gonad weight of the sea urchin Mesocentrotus nudus were examined monthly from March 2015 through December 2018. The kelp was abundant and the gonad index (= gonad ∕ body weight × 100) of the sea urchins reached more than 20% in 2015. However, in the following 3 years (2016 to 2018), the kelp was nearly absent from the area and the maximum gonad index was significantly less than that in the kelp-abundant year (2015). During the kelp-scarce 3 years, the gonad index showed a significant decrease from one kelp-scarce year to another, indicating that the effect of a poor algal growth on the gonad production of sea urchins was cumulative over the following years.

Relationship between empirical water temperature and spring characteristics of swordtip squid (Uroteuthis edulis) caught in the eastern Tsushima Strait

ABSTRACTWe analysed the data of swordtip squid Uroteuthis edulis caught in the eastern Tsushima Strait, from April to September between 2012 and 2018, to consider the relationships among mantle length and body and gonad weights, associated with the estimated seasonal migratory routes and itineraries improved by the quantitative results of the tracer experiments. Our analyses have enabled us to reveal the characteristics of kensaki-type squid and the reasons for their appearance. We identified the kensaki-type U. edulis as male individuals, caught mainly in April–June, with long slender bodies, probably adapted to empirical duration of the cold sea water temperature in the Sea of Amakusa. Researchers and fishermen have referred to the seasonal migrating group including such males as a spring-migrating group. However, the females belonging to the spring-migrating group had no kensaki-type characteristics. Moreover, contrary to that achieved by the males, the female squid had acquired greater maturation in the spring than in any other seasons. These data demonstrated that the females continued to grow to maturation even in the cold sea waters, implying a different female strategy for reproduction from that of male squid. We are concerned that the commercially valuable kensaki-type squid may decrease in the future because the water temperature in the northern East China Sea is gradually rising, probably due to global climate change.

Gonad quality of sea urchin Tripneustis gratilla with different seaweed diets

ABSTRACT
 
 Gonad quality of sea urchin Tripneustis gratilla is influenced by consumed seaweed type. Therefore, this study was conducted to determine the type of seaweed as potential source of carotenoids and produce a good quality of sea urchin gonad. The study was conducted in two phases, namely first phase was to obtain the content of carotenoids and β-carotene from several species of seaweed; and second phase was to testify the seaweed that produced high quality of sea urchin gonad.This study used completely randomized design with 4 treatmens of macroalgae diets, namely: 1. Enhalus sp., 2. Sargassum sp., 3. Ulva sp., and 4. Eucheuma sp. Each treament was repeated three times. Measured parameters were gonad weight, gonad maturity index, gonad color quality, and gonad texture. The study result showed that Enhalus contained the highest carotenoid and β-carotene content with 1409.53 and 639.37 mg/kg respectively. The highest gonad weight was 2.8 g; gonad color and texture was good (score 3); and the highest gonad maturity index was 5.4% that obtained from sea urchin fed with Enhalus. Therefore, this study concludes that Enhalus is potential source of carotenoids for sea urchin T. gratilla diet that will produce a good quality of gonad.
 
 Keywords: carotenoid, diet, gonad quality, sea urchin, seaweed.

Fecundity estimation of Indian Potasi, Neotropius atherinoides in Bangladesh

Fecundity estimation has obvious significance in aquaculture, since the size of brood stock, amount of rearing facilities and necessity of other equipment’s are dependent on fecundity. The study has been conducted on fecundity estimation of Indian potasi, Neotropius atherinoides, based on 202 females collected from the Kangsha River flowing through Netrokona district during the period from January to June 2013. The standard length (SL) range of female were 47-66, 50-64, 57-68, 50-66, 56-66 and 60-76 mm and range of body weight were 1.07-3.56, 1.23-3.35, 2.36-3.81, 1.69-4.31, 2.33-5.59 and 3.18-5.14 g in January, February, March, April, May and June, respectively. The mean Gonado somatic indices (GSI) were very low from January to March but these were abruptly high during subsequent three months. Based on mean GSI the spawning season of this species was assumed from April to June over the study period. Scatter plot of standard length with corresponding GSI revealed that the minimum length of mature female was 50 mm SL. Egg diameter frequency distribution of a mature ovary showed almost only one major mode of egg size suggested that the fish is a single spawner, and summation of eggs in that mode was regarded as the fecundity of a female Indian potasi. The regression equation of the relationship between standard length and fecundity was as, Fecundity = 0.0017 SL 3.55. The relative fecundity and the absolute fecundity of a fish having SL of 62 mm was 1477 per g and 3921, respectively based on F-SL relationship. The relationship between body weight and fecundity was as, Fecundity = 1371.3 BW-650.8. The absolute fecundity of a fish having BW of 3.51 g was 4162 respectively based F-BW relationship. The relationship between ovary weight and fecundity was as, Fecundity = 6244.3 OW + 967.52. The absolute fecundity of a fish having ovary weight of 3.51 g was 7211 based F-OW relationship. The correlation coefficient of all above analyses were very high (>0.755) attributing that standard length, body weight and gonad weight were highly positively correlated with fecundity of Indian Potasi, Neotropius atherinoides.
 Res. Agric., Livest. Fish.6(3): 421-429, December 2019

Influence of the myotome zone and sex on the muscle cellularity and fillet texture of diploid and triploid turbots Scophthalmus maximus L.

The muscle and textural parameters were analyzed in four myotome zones (epaxial upper, hipoaxial upper, epaxial bottom, and hipoaxial bottom) in seven diploids (D) and seven triploids (T) turbot specimens. Diploid specimens showed the highest values of the size and number of white fibers in the epaxial zones, being such values higher in female than male specimens. In triploid specimens, the highest fibers sizes were found in the upper zones (epaxial and hipoaxial), whereas the lowest number and density of fibers were found in the epaxial upper zone. In this latter group (T), the lowest fibers sizes were found in female specimens, whereas the rest of the parameters were usually higher in female than male specimens. When comparing both groups, the hypertrophy was higher in T than D in all zones. In both ploidy groups, the highest textural values were usually observed in the upper epaxial fillet, being slightly higher in female than male specimens. The values of standard length, total weight, gonad weight, gonadosomatic index and gutted weight were higher in female than male specimens in both groups (D and T).

ЗАКОНОМЕРНОСТИ ПОЛОВОГО СОЗРЕВАНИЯ ТИХООКЕАНСКОЙ СЕЛЬДИ CLUPEA PALLASII (VAL.) НА ПРИМЕРЕ КОРФО-КАРАГИНСКОЙ ПОПУЛЯЦИИ

Analysis of field and laboratory identifications stages of gonad maturity was carried out for 1960–2017. The dynamics of the gonad size and weight and of the gonad-somatic index during maturation were studied. The size structure and the condition of herring oocytes in the ovaries of different stages of maturity was figured out. Seasonal maturation was considered.

Impacts of the alien mosquitofish on the abundance and condition of two Mediterranean native fish

The rapid decline of the Greek native Valencia letourneuxi, and its recently described sister species Valencia robertae, has been often attributed to habitat degradation, as well as aggression from or resource competition with the alien mosquitofish Gambusia holbrooki. The mosquitofish is extremely wide-spread in Mediterranean freshwater ecosystems, however, documentation on its presumed negative impacts on native freshwater fishes is limited. In this study, we compared abundance, condition and gonad weight of Valencia spp. in no co-occurrence versus co-occurrence to the mosquitofish, using data collected from eight aquatic systems of Greece, over a five year period (2005 to 2009). Our results show that Valencia abundance is significantly lower in co-occurrence to the Eastern mosquitofish. Furthermore, female Valencia spp. individuals in co-occurrence to the mosquitofish were smaller in length and had poorer somatic condition compared to females in habitats not invaded by the mosquitofish. The mechanisms responsible for these effects of the alien mosquitofish as well as the conservation implications for native Valencia populations are discussed.

Effects of omega-3 on androgenic activity in cadmium-induced hypertensive rats

Background and objective: Cadmium is a widely distributed metal in the environment that causes testicular toxicity and various tissue damage associated with hypertension. Omega-3, an essential fatty acid, has been demonstrated to be an effective antioxidant and anti-inflammatory agent. This study aimed to investigate the toxic effects of cadmium on cardiovascular and reproductive systems in male rats and examine the possible protective effects of omega-3 against cadmium-induced hypertension and testicular dysfunctions. Methods: The rats were divided into three groups. The first group served as the control, the second group received cadmium chloride in drinking water, and the third group received cadmium chloride plus omega-3 for 28 days. Blood pressure and heart rate were estimated. Blood samples were collected; sexual hormones and other biochemical parameters were evaluated. Testes and epididymis were taken for semen analysis and histopathology. Results: Significant adverse effects were seen in the studied parameters of the cardiovascular and reproductive systems after cadmium exposure, including hypertension, alteration in sperm parameters, weights of sex glands, and histological structures. In contrast, co-administration of omega-3 significantly reduced mean blood pressure, but improved sperm parameters and the histology of testis. No protective effect of omega-3 could be seen on male hormone and lipid profile parameters except high-density lipoprotein. Conclusion: Exposure to cadmium induced hypertension, impaired testicular functions, and histology. Omega-3 has protective effects on vascular and testicular functions. Therefore, supplementation with omega-3 had a protective effect against cardiovascular and reproductive toxicity induced by cadmium.

Low dose prenatal testosterone exposure decreases the corticosterone response to stress in adult male, but not female, mice

Gonadal steroid hormones affect the organization of the brain during sensitive periods of development, resulting in sex differences in the neuroendocrine function and behaviour of the offspring. Although alterations in developmental testosterone exposure have been hypothesized to play a role in male-biased neurodevelopmental disorders, the underlying mechanisms remain unknown. The present study investigated the hypothesis that early prenatal exposure to low concentrations of testosterone might affect the control of stress responses in later life. Pregnant CD1 mice were treated with 10 μg of testosterone propionate or sesame oil control on embryonic days 12, 14, and 16. Effects on development were assessed by measuring litter size, composition and weight, first appearance of hair, eye and ear opening, and adult body weight. Reproductive development was assessed by measuring testosterone levels in neonatal and adult males, gonad weights in both sexes and reproductive cyclicity in females. The function of the hypothalamic-pituitary-adrenal axis was determined by measuring corticosterone in hair samples from juvenile animals, as well as in plasma following restraint stress in adulthood. Prenatal testosterone treatment had no significant effects on any of the overall developmental or reproductive endpoints assessed. However, in adulthood, corticosterone responses to restraint stress were reduced in the male but not the female offspring, with no significant effect on basal corticosterone levels in either sex. Thus, a small prenatal increase in maternal testosterone may be sufficient to produce a lasting sex-specific alteration in the sensitivity of the male HPA axis to stress.

POPULATION ASPECTS AND RECRUITMENT OF Odontostilbe paraguayensis (CHARACIFORMES: CHARACIDAE) IN THE PARAGUAY RIVER, PANTANAL, BRAZIL

Population dynamics allows comprehension on how population assures its success on continuity of the species and the balance of its population density. Thus, in order to analyze reproductive parameters (i.e., gonadal maturation stages, fecundity, and recruitment) and population aspects (i.e., length-weight frequency, asymptotic length, growth and mortality rates, and sex ratio) of Odontostilbe paraguayensis Eigenmann & Kennedy (1903) (Characiformes: Characidae) in the southern Pantanal of Brazil, samples were carried out from February 2009 to January 2011 along the main channel of the Paraguay River and its tributary, the Amonguija River, with seine net and a rectangular sieve (0.8 x 1.2 m). To estimate population parameters, the data of 604 individuals were recorded, and for reproductive aspects, the data of 394 individuals were recorded. The sex ratio was 3:1 (females:males). The estimated asymptotic length (L∞) was 36.67 mm. The population had high growth rate values (k = 1.3 year-1) and mortality (Z = 1.98). Longevity was estimated as 2.3 years. The mean absolute fecundity was 420.2 oocytes/female. Absolute fecundity was positively related to total weight (g) and gonad weight (mg). For females, the standard length at first maturity (L50) was 24.1 mm, and for males, it was 27.6 mm. Reproducing females were more frequent in March and April, although females with ripe gonads were recorded nearly all year long. The recruitment pattern was long with positive correlation with the average historic level of the Paraguay River, considering seasonal flooding. The lengthweight relationships were not different between the sexes, but they presented negative allometric growth. Thus, during ontogeny, the species presents more increment in length than in weight, and, consistent with the high growth rate, this may be understood as a way to reach longer lengths faster to avoid predation. The outcomes demonstrate that O. paraguayensis has a short life cycle with high growth and mortality rates. Together with the long recruitment pattern and high fecundity, the species may be considered an r-strategist.

Gonadosomatic Index, Oocyte Development and Fecundity of the Snakehead Fish (Channa striata) in Natural River of Mae La, Singburi Province, Thailand.

Reproductive cycle of snakehead fish (Channa striata) is necessary to inform management plans of the natural fish. This work aimed to study the gonadosomatic index (GSI), oocyte development and fecundity of C. striata in the Mae La River, Singburi province, Thailand from November, 2017-October, 2018. GSI was calculated from gonadal weight and body weight. Ovarian sections derived from standard histological methods were used to evaluate oocyte development, respectively. Fecundity was measured using the gravimetric method and the relationships of fecundity-total length, fecundity-body weight and fecundity-ovarian weight were evaluated. The highest average GSI values for females and males were found in July (6.15±0.20 and 0.14±0.12, respectively). Ovarian histology revealed 4 stages of ovarian development: (1) immature, (2) maturing, (3) mature and (4) spent. Stages 1, 2, 3 and 4 were observed for 11, 10, 6 and 2 months, respectively. The highest percentages of immature, mature and spent oocytes were found in October (93.33%), July (89.56%) and August (33.33%), respectively. Fecundity ranged from 4,160-46,890. Fecundity varied depending on total length, body weight and ovarian weight, with correlation coefficients (R) of 0.986, 0.960 and 0.989, respectively. Oocyte maturation period of C. striata occurs from April to August. The highest gonads development was in July. Fecundity exhibited linear relationships with body length, body weight and ovarian weight.

Photoperiodic effects in blood glucose, cortisol, hematological parameters and reproductive indexes of gift lineage reversed male tilapia

The objective of this study was to evaluate the influence of the photoperiod on the physiological, hematological and reproductive parameters of tilapia males of the GIFT lineage. The treatments differed in the simulations of emeral photoperiods T1 = 0L: 24E T2 = 24L: 0E, T3 = 12L: 12E. Each aquarium was considered an experimental unit. In the present study, tilapia males under different photoperiods did not present significant differences in gonad weight and gonadosomatic index. At the end of the experiment, there were also no significant differences in hepatosomatic indexes (IHS) of Tilapia males under different treatments. In the present experiment, it was observed that the 0L: 24E treatment obtained a shorter testicular length in relation to the other treatments. In addition, the Tilapia submitted to 24L: 0E presented significant difference for the glucose levels, and did not present significant difference for cortisol levels and survival rate compared withthe other treatments. There were no statistical differences for hematological values. Exposure to different light regimes has shown that for GIFT tilapia, the photoperiod that promotes better reproductive index and well-being conditions is the photoperiod (12L: 12E).

Ege Denizi’nde (Akdeniz) Holothuria polii (Delle Chiaje, 1823) türü deniz hıyarının yumurtlama dönemindeki gonad gelişimi

The Mediterranean sea cucumbers including Holothuria polii has become commercially important in international trade due to the high demand of consumers from Far East countries. Sea cucumbers fisheries is a valuable income for the regional fishermen but natural stocks endangered by overfishing in recent years. Fisheries regulations and aquaculture studies are important precautions for preserving natural stocks. All these efforts are based on reproduction biology of this species which slightly differed among regions. In this study, the reproduction biology including morphological characteristics, gonadosomatic index and gonadal development stages of H.polii at the eastern coast of Aegean Sea (Izmir, Turkey) were investigated during the reproduction (spawning) period from July to October 2018. Gonads and gonad sections of 60 sea cucumbers (120.60 ± 19.56 g) have been observed by macroscopic and microscopic inspections. Three gonadal development stages have been identified by histologic observations as mature (III), spawning (IV) and post-spawning stage (V) in gonadal tubules. Results indicate that both female and male gonads are at mature and spawning stage in July and all gonads are at post-spawning stage in October. The mean gonad weight was 12.53 ± 1.33 g at the beginning of the spawning period (July) and 1.87 ± 0.58 g at the end of the spawning period (October). Gonadosomatic index decreased from 17.53 ± 0.02% (July) to 3.37 ± 0.01% (October) after spawning. The gonadosomatic index, gonad weight, and spawning were related to the seawater temperature. According to this study, the spawning period of H.polii at the eastern coasts of the Aegean Sea starts in July and completely ends in October. As a result, the data related to the reproduction biology in spawning period of H.polii would guide stock management and artificial breeding of this species under controlled conditions.

PENGARUH PEMBERIAN HORMON 17β-ESTRADIOL TERHADAP PERKEMBANGAN GONAD SIPUT GONGGONG Laevistrombus turturella

Siput gonggong Laevistrombus turturella semakin intensif ditangkap sehingga populasinya di alam menurun. Upaya budidaya gonggong diperlukan untuk menjaga populasinya. Teknologi reproduksi siput belum banyak dikembangkan di Indonesia. Keberadaan 17β-estradiol pada siput dan moluska lain telah dinyatakan oleh beberapa peneliti, namun perannya dalam proses reproduksi siput belum banyak diketahui. Penelitian tentang pemberian 17β-estradiol untuk memacu perkembangan gonad gonggong belum pernah dilaporkan. Penelitian ini bertujuan mengaji pengaruh pemberian 17β-estradiol terhadap perkembangan gonad gonggong. Ada tiga perlakuan yang diberikan pada tiga kelompok gonggong, yaitu masing-masing tanpa suntikan (P1), suntikan 30 µL/ekor larutan minyak jagung dan etanol absolut (P2), serta suntikan 30 µL/ekor larutan 17β-estradiol (P3). Pascasuntikan, gonggong dipelihara dalam pensculture di habitat alaminya selama 30 hari. Hasil penelitian menunjukkan bahwa perlakuan suntikan larutan 17β-estradiol (P3) menstimulasi perkembangan gonad gonggong yang dibuktikan dengan nilai rata-rata ukuran diameter oosit yang lebih besar daripada perlakuan lain. Nilai rata-rata bobot gonad dan GSI perlakuan P3 juga lebih besar dibanding perlakuan P1 dan P2. Analisis SDS-PAGE menunjukkan hemolimfa gonggong memiliki beberapa jenis protein dengan berat molekul bervariasi. Protein dengan berat molekul 54-55 kDa diprediksi sebagai vitelogenin gonggong.
 

Growth pattern and maturity level of Chevron Snakehead’s gonad (Channa Striata)

Chevron Snakehead (Channa striata) is one kind of freshwater fish that has high nutrient content, particularly albumin. Chevron Snakehead is mostly found in public waters and has not cultivated extensively. This research was aimed to investigate the behaviour, the biological features, the maturity level of gonad, and the growth pattern of Chevron Snakehead. This research was conducted in Tukad Yeh Sungi and irrigation canal of Subak Baru in Baturiti Sub-district, Tabanan Regency in 30 September until 27 October 2017 by using observation, descriptive, and analitical methods. Chevron Snakehead which was found in this research was Channa striata that mostly found in deeper waters with rocky or sandy substrates. This fish is included into nocturnal and carnivora. b. based on the maturity of the gonads of male Chevron Snakehead the testicular weight was 0.1-0.85 gr. Whereas for females it has a gonadal weight of 0.5-1.86 gr. Chevron Snakehead found in rivers have allometric growth patterns, with b values obtained <3 which are b values of females = 2.8696 and b values of males = 2.3335, therefore the growth pattern of Chevron Snakehead was allometric negative. Negative allometric is the dominant increase in on weight gain.

Maturity assignment based on histology‐validated macroscopic criteria: Tackling the stock decline of the Mediterranean swordfish (Xiphias gladius)

Abstract Effective stock assessment relies on the evaluation of the reproductive potential of a population, but this is often achieved using fast, inexpensive, and inaccurate macroscopic indicators of gonadal maturity. Indeed, this approach suffers from high error rates as a result of misclassification and operator errors. Although histology is considered the gold standard to assign reproductive stages, it represents a time‐consuming and expensive method. Therefore, cost‐effective approaches are currently needed to assess the species‐specific reproductive potential and define the correct size at first maturity (L50). In the present study a histology‐calibrated method based on the gonadal index (GI) was developed to assign maturity stages to the overfished Mediterranean swordfish (Xiphias gladius), supported by histological classification of gonadal development, an estimation of L50, and an analysis of the reproductive output of this species. The performance of this new method had an overall agreement of 90% with histological data, and the L50 calculated by the GI‐based method compared with histology analysis was not statistically different (p &gt; 0.05). Moreover, in order to apply this method without bias, a thorough validation of the relationship between length and gonad weight was carried out and the suitability of the GI to compare individuals of different size and maturity stages was confirmed. The present findings provide a comprehensive picture of the patterns characterizing Mediterranean swordfish reproduction and a promising method to assign maturity stages based on a macroscopic indicator. This method has the potential to be extensively applied during routine fish sampling activities in the field because of its simple requirements.

Evaluation of Genomic Selection for Seven Economic Traits in Yellow Drum (Nibea albiflora)

Yellow drum (Nibea albiflora) is an important maricultural fish in China, and genetic improvement is necessary for this species. This research evaluated the application of genomic selection methods to predict the genetic values of seven economic traits for yellow drum. Using genome-wide single-nucleotide polymorphisms (SNPs), we estimated the genetic parameters for seven traits, including body length (BL), swimming bladder index (SBI), swimming bladder weight (SBW), body thickness (BT), body height (BH), body length/body height ratio (LHR), and gonad weight index (GWI). The heritability estimates ranged from 0.309 to 0.843. We evaluated the prediction performance of various statistical methods, and no one method provided the highest predictive ability for all traits. We then evaluated and compared the use of genome-wide association study (GWAS)–informative SNPs and random SNPs for prediction and found that GWAS-informative SNPs obviously increased. It only needed 5 and 100 informative SNPs for LHR and BT to achieve almost the same predictive abilities as using genome-wide SNPs, and for BL, SBI, SBW, BH, and GWI, about 1000 to 3000 informative SNPs were needed to achieve whole-genome level predictive abilities. It can be concluded from the test results that breeders can use fewer SNPs to save the breeding costs of genomic selection for some traits.