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1.
Demography can have a significant effect on reproductive timing and the magnitude of such an effect can be comparable to environmentally induced variability. This effect arises because the individuals of many fish species spawn progressively earlier within a season and may produce more egg batches over a longer period as they get older, thus extending their lifetime spawning duration. Inter‐annual variation in spawning time is a critical factor in reproductive success because it affects the early environmental conditions experienced by progeny and the period they have to complete phases of development. By reducing the average lifetime spawning duration within a fish stock, fishing pressure could be increasing the variability in reproductive success and reducing long‐term stock reproductive potential. Empirical estimates of selection on birth date, from experiments and using otolith microstructure, demonstrate that there is considerable variation in selection on birth date both within a spawning season and between years. The few multi‐year studies that have linked egg production with the survival of progeny to the juvenile stage further highlight the uncertainty that adults face in timing their spawning to optimize offspring survival. The production of many small batches of eggs over a long period of time within a season and over a lifetime is therefore likely to decrease variance and increase mean progeny survival. Quantifying this effect of demography on variability in survival requires a focus on lifetime reproductive success rather than year specific relationships between recruitment and stock reproductive potential. Modelling approaches are suggested that can better quantify the likely impact of changing spawning times on year‐class strength and lifetime reproductive potential. The evidence presented strengthens the need to avoid fishing severely age truncated fish stocks.  相似文献   

2.
We evaluated the annual process of oocyte and ovarian development of the planktivorous Amazonian catfish, the mapará (Hypophthalmus marginatus), aiming to support captive reproduction for domestication. A total of 149 females were captured from the Tocantins River at the Tucuruí Dam (3°49'55"S, 49°39'9"W) in 13 sampling events. For each individual, we evaluated ovary histology and plasma steroid concentrations. Two annual reproductive cycles, with similar characteristics, including a long period of rest, a short vitellogenic stage and a well‐defined spawning season from November to March, were described. A 17β‐estradiol (E2) rise and a 17α,20β‐dihydroxy‐4‐pregnen‐3‐one (DHP) peak were associated with vitellogenesis and spawning season, respectively, in the first cycle but not in the second reproductive cycle. In conclusion, the studied species presents a reproductive cycle similar to that of other migratory total spawners; however, unusually for this group of fish, there were three (but not two) batches of vitellogenic oocytes in “in maturation” and “mature” stage ovaries, pointing to the possibility of more than one spawn during the spawning season.  相似文献   

3.
Skipped spawning in female iteroparous fishes   总被引：10，自引：0，他引：10  
It is often assumed that iteroparous fishes spawn annually once reaching sexual maturity, but this is not always the case. This paper reviews available information on skipped spawning in female teleost fishes. All instances of non‐annual spawning are described as one of three types (retaining, reabsorbing, resting), depending on where in the normal spawning cycle development has been interrupted. Retaining ripe eggs is caused by conditions experienced during the spawning season (fish density, mate availability, pollution), whereas failure to start vitellogenesis (resting) or the breakdown of all oocytes that enter into vitellogenesis (reabsorbing) is caused by factors experienced prior to the spawning season (primarily temperature and poor nutrition). It is speculated that the relative shortage of data on non‐annual spawning may be because of difficulties in identifying non‐reproductive individuals. In an attempt to rectify this situation, the criteria needed to identify females undergoing the three forms of spawning omission are presented in terms of external appearance of gonads, gonad indices, and histological analysis. The energy saved by not spawning in a poor year may lead to increased survival and the probability of spawning in subsequent years. As the cumulative number of progeny gained by surviving to spawn in multiple subsequent years outweighs the number of progeny lost by not spawning in a given single year, occasional omission of spawning may constitute an adaptive trait in long‐lived iteroparous fishes.  相似文献   

4.
The interspecific hybridization of channel catfish, Ictalurus punctatus, females with blue catfish, I. furcatus, males has been identified as a method to further improve production; however, lack of spawning success has affected its commercial application. To facilitate our understanding of the interaction of brood stock nutrition and reproductive performance, we evaluated the interaction of feed quality and feeding frequency. Channel catfish females were classified into two genetic groups, namely, high and low spawning. The treatments were offered during the spring season 70–90 d prior to the start of the spawning season. Induced reproduction was performed using luteinizing hormone releasing hormone analog. Condition of the fish as well as reproductive performance using spawning success, egg production, egg size, and fertilization at 48 h were determined. Changing protein level of the diet from 32 to 42% did not influence spawning, fecundity, or fertilization, but affected egg size and biochemical composition of the eggs. Increasing the feeding frequency from three to six times per week negatively affected spawning in one of the two genetics groups, did not affect egg production and egg fertilization, but had a significant effect on egg size. Older fish performed better than younger fish in terms of spawning success and egg production.  相似文献   

5.
This study investigated supplemental effects of vitamin A in diet on reproduction of Japanese flounder Paralichthys olivaceus (T & S). Broodstock were fed either a non‐supplemented diet (control diet; CD) or a vitamin A‐supplemented diet (supplemental diet; SD) 1 month before and during the spawning season. Both dietary groups began to spawn in mid‐January. At the beginning of spawning, no notable differences were found in spawning or egg quality between treatments. Egg production of the CD broodstock began to decrease from mid‐April and spawning stopped in late May, whereas the SD group continued to spawn until the end of June. Buoyant egg rate of the CD group was lower than that of the SD group throughout the spawning period. Hatching rate was not different between the CD and SD groups. The percentage of normal larvae in the CD group was significantly lower than in the SD group. It is concluded that a low vitamin A content in the diet has some negative effects on reproduction of flounder. The importance of supplementation of vitamin A in broodstock diet of the Japanese flounder is suggested.  相似文献   

6.
2013年8月至2014年7月,采用组织学和实验生态学方法对钝缀锦蛤(Tapes conspersus)的性腺发育、生殖周期、肥满度、胚胎和幼虫发育进行了研究。结果显示,钝缀锦蛤性腺发育以1年为1个周期,性腺发育过程可分为增殖期、生长期、成熟期、排放期和休止期5个时期;繁殖期在每年10月至翌年3月,繁殖盛期为3月、10月和11月(水温20.3~24.6℃),分批产卵。8月肥满度最高,为33.43%;4月最低,为18.31%。钝缀锦蛤卵径为70~80μm;在水温24~26℃、盐度28~32条件下,受精卵经16 h左右发育为D形幼虫;初孵D形幼虫大小为90~110μm,浮游幼虫经7~8 d培育进入附着变态期,此时壳长为210~230μm,再经4~5 d发育变态为稚贝。本研究为钝缀锦蛤的人工繁育及种质资源保护和利用提供了基础资料。  相似文献   

7.
Multiple spawnings are special reproductive tactics that many fish evolved to obtain different types of direct and/or indirect spawning benefits. This has led to two pertinent questions: (a) what types of benefit does a commercially important fish provide during multiple induced spawnings annually? and (b) is there any trade‐off between traits during these spawnings? To address these questions, the present study was carried out with two separate experiments during two spawning events of an Indian major carp (Catla catla) to assess: (a) male's spawning performances and (b) female's spawning performances. The male's spawning data revealed that they produced significantly higher amount of milt and hatchlings during the first spawning, while they significantly reduced hatchling deformation rate, enhanced offspring survival rate and enlarged offspring body size during the second spawning. The female's spawning information unveiled no significant differences in total egg weight, hatching rate and hatchling deformation rate between the first and second spawning. However, females had significantly higher offspring survival rate during the first spawning and enhanced offspring body size during the second spawning. Interestingly, the analysis of trait associations revealed that males allocated energy with a trade‐off between milt weight and offspring survival rate, whereas females showed a trade‐off between hatching rate and offspring survival rate. Thus, the study provides some important information for carp breeders and associated stakeholders to know which spawning season is preferable for the higher production of eggs, milt and good quality larvae.  相似文献   

8.
Timing of reproduction is an important life‐history trait that varies among species as a function of energy allocation strategy, particularly as individuals are influenced by seasonal variations prior to and during the reproductive season. This study investigated size‐ and sex‐based seasonal patterns of energy allocation in bluegill, Lepomis macrochirus (Rafinesque), a species that spawns repeatedly throughout the summer, by quantifying gonad, liver and mesenteric fat masses. Results indicate that bluegill delay production of gonad tissue until the onset of the spawning season and use an ‘income spawning’ approach. Comparisons of energetic trends with crappies, Pomoxis annularis (Rafinesque) and P. nigromaculatus (Lesueur), a confamilial species of relatively similar size and morphology that spawns in the spring, highlight the flexibility of energy allocation patterns even among relatively similar fishes and shed light on bluegill life‐history strategies.  相似文献   

9.
Nutritional components and feeding strategies are multifarious amongst different producers, whereas they are just designed for fish farming but not suitable for improving the reproductive performance of broodfish. Yellow catfish (Pelteobagrus fulvidraco), an omnivorous species, is one of the important aquaculture fish in China. In order to improve the reproductive performance of female yellow catfish (119.86—134.54 g), four feeding strategies (0.5%, 0.75%, 1% and 1.5% BW/d) and three dietary protein levels (34%, 40% and 46%) were examined, respectively, in the two separate trials. The females with moderate feed restriction (1%) showed significant lower mesenteric fat index (MFI) and higher gonadosomatic index (GSI) than the satiation group (1.5%) and excessive feeding restriction groups (0.5% and 0.75%). Females with high MFI were difficult to be artificially propagated and showed a high mortality rate, whilst the fish at 1.0% feeding rate displayed low mortality rate and high ratios of spawned fish, as well as high percentages of fertilization and hatching. Meanwhile, the offspring of 1.0% feeding rate group showed a low malformation rate and high survival rate. Multiple spawning in the same breeding season are applied in yellow catfish to reduce the number of parent fish and increase the fry production, and gonadal recrudescence after spawning might be affected by different nutrient values including dietary protein levels. In the second trail, female yellow catfish were fed with 34%, 40% and 46% crude protein diet at 1% feeding rate for the second spawning, and the best reproductive and breeding performances were observed in the fish group with 46% crude protein diet. These results demonstrate that 1% feeding rate is optimum for the spawning and reproductive performance of female yellow catfish for the first artificial spawning, and 46% dietary protein group had the best reproductive performances in the second spawning.  相似文献   

10.
The fathead minnow, Pimephales promelas, is widely used as a bait, forage, and research fish in the United States. A hardy and fecund fish, this species has many attributes that are excellent for culture. Unfortunately, despite the widespread use of fathead minnows in toxicity testing and thousands of resulting publications, relatively little aquaculture‐related research has been conducted in support of commercial production. On the surface, current commercial fathead minnow production practices appear much the same as those of a decade ago. However, producers continue to refine culture methods, balancing broodfish stocking rates, spawning substrate quantity, and feeding rates in an attempt to meet both losses to predators and market demand. This review examines relevant reproduction‐related studies in the fields of ecology, behavior, toxicology, and aquaculture with the goal of advancing fathead minnow culture. In fathead minnow production, relative to the culture of food fish species, reproduction is vital, more so than rapid growth or a low feed conversion ratio. Fish numbers may exceed 1 million fish/ha, while feeding rates are relatively low and in feeder fish production, growth is deliberately restrained in order to maintain fish within market sizes year‐round. Underappreciated factors identified as affecting reproduction and with implications for commercial culture include: (a) poor egg adhesion to commonly used spawning substrates, (b) egg and fry cannibalism at high fish densities, and (c) the relatively short breeding period of individual males. Results highlight the importance of selecting an appropriate broodfish stocking rate based on fish size, anticipated pond fertility, and feeding program. New methods to improve reproductive performance will likely increase costs and will need to be accompanied by thorough economic analyses.  相似文献   

11.
This study reports egg production by captive wild brill Scophthalmus rhombus, a potential new flatfish species for Southern Europe‐Mediterranean mariculture, as well as seasonal plasma levels of 17β–estradiol, testosterone, 11–ketotestosterone, proteins, triglycerides, glucose and lactate. A mean egg production of 102 800 eggs kg body weight−1 was achieved during the 2005 spawning period (January–March), although a continuous egg supply could only be obtained from some females, which had a higher relative fecundity (261 019±10 393 eggs kg−1) with 12–17 eggs batches released at a mean interval of 3.4 days. Most eggs were obtained with water temperatures ranging from 12 to 14°C, and under increasing temperatures (up to 2.9°C). Potential egg viability (70.1±2.9%), fertilization (72.2±3.4%) and hatching rates (31.9±3.9%) showed high variability, with potential viability tending to decrease as the water temperature increased (mainly between 16 and 17°C) and 0% hatching above 16.6°C. The endocrine changes that brill underwent during late gametogenesis, spawning and postspawning periods were similar to those reported in other Pleuronectiformes. This study establishes an important basis for further research on the biology and physiology of brill reproduction, directed towards the optimization of the breeding techniques used currently.  相似文献   

12.
A set of five variable microsatellite markers was used for the genetic characterization of two common dentex ( Dentex dentex ) broodstocks from an experimental hatchery and for the screening of the egg batches spawned during the complete spawn season in 2006. After parentage assignment, simulations were performed for the hatchery 1 broodstocks; the microsatellite set correctly assigned over 93% of descendants to parents when one parent was known and 80% when neither parent was known. Of the 261 eggs that the DNA was correctly amplified from, 254 were successfully assigned to a parental couple. More than one female or male took part (at the same point in time) in the spawning season. However, we observed 'dominant' individuals that produced high proportions of the descendants (unequal reproductive success) in all the sampling periods, although the contributions of these dominant individuals could change over time. This phenomenon reduces the effective breeding numbers, and could lead to inbreeding if this factor is not taken into account when the next parental generation is obtained. This factor should also be considered in aquaculture selection programmes because the dominant breeders may not be the most interesting individuals for commercial or productive schemes.  相似文献   

13.
Nine trials were carried out on the induced propagation of pike perch in out‐of‐season as well as in the natural reproduction period. From January till May, periodically, 16–20 pairs were transported to the hatchery, and acclimated to 15–16°C. The following hormonal treatments were used to induce reproduction: carp pituitary homogenate (CP) and human chorionic gonadotropin (hCG) alone or in combination; gonadotrop‐releasing hormone ‘Ovurelin’ (D‐Phe6‐LH‐RH) alone or with metaclopramid (MTC); and ‘Ovopel’ [containing des‐Gly10‐(D‐Ala6)‐LH‐RH‐ethylamide and MTC]. The effects of daylight regime, water temperature and the length of the pre‐spawning conditioning period on the reproduction performance were determined. From the 130 hormonally treated pairs, 122 either spawned in tanks or were stripped. There were no differences in the ovulation rate between out‐of‐season (93%) and seasonal (91%) propagation. The developmental stage of the eggs correlated with the latency period, which significantly declined from January till April. The latency period was the shortest in fish treated with hCG and, secondly, with CP. The germinal vesicle migration did not proceed without hormonal treatment, although in some trials breeders were kept at the spawning temperature for 1–2 weeks. The results demonstrate that the pike perch can be successfully induced to spawn about 3 months earlier than its natural spawning season, which allows a significantly prolonged yearly supply of fry.  相似文献   

14.
Cues from the moon influence synchrony in growth, feeding, migration, behaviour and reproduction of many reef fishes. Compared with comprehensive studies on the annual and daily activities of fish, few physiological studies have paid attention to the importance of lunar cues in reproductive activities. We review mutual and interesting relationships between fish reproduction and environmental changes induced by the moon, with particular emphasis on the reproductive activity of the rabbitfishes (Siganidae). Rabbitfish species exhibit, in nature, a definitive reproductive season, which differs among the tropical areas. During the reproductive season, synchronous spawning of rabbitfish is associated with a particular lunar phase. The lunar phase used by the respective species is similar in different regions on the earth. Histological observations revealed that gonads develop synchronously towards a peak around the spawning lunar phase, after which the gonads return to spent condition. Concomitant with gonadal development, sex steroid hormones were produced under the influence of gonadotropin (GtH). Injections of human chronic gonadotropin (hCG) to the fish that are undergoing active spermatogenesis accelerated testicular maturation. These results suggest that hormonal response in maturing the gonads in rabbitfish is under the regulation of GtH, and that pituitary secretion of GtH according to the lunar cycle accounts for the lunar rhythm in gonadal development. We speculate that the cues from the moon can be recognized by the higher parts of the hypothalamus–pituitary–gonadal axis. Possible relationships between exogenous environmental factors and the lunar‐reproductive rhythm are also discussed.  相似文献   

15.
Hogfish, Lachnolaimus maximus (Walbaum), have multiple traits that confound measuring reproductive potential: they are protogynous, relatively long‐lived harem‐forming fish that spawn daily for months. Additionally, recent evidence demonstrates that size, age and timing of sex change vary on a spatial scale within the study area (West Florida shelf, USA). This study investigates the effect of this spatial variation on hogfish reproductive potential by evaluating spawning seasonality, spawning frequency and batch fecundity using an indeterminate egg production model. Offshore females were larger than nearshore females, and batch fecundity was related in a log‐linear manner to female size. Gonad histology demonstrated a more protracted reproductive period for females offshore (8 months) than nearshore (4 months). Spatial variations in size coincide with ontogeny because hogfish move offshore with growth; however, even after accounting for fish size, offshore females spawned more. In areas where male removal rates are elevated, spawning harems are disrupted; thus, greater fishing effort nearshore may further reduce the reproductive potential of these females. These nearshore and offshore spawning components of the population are not genetically distinct, but instead represent two contingent spawning strategies that likely enhance total population stability and resilience of this stock in the eastern Gulf of Mexico.  相似文献   

16.
Abstract – We examined the reproductive characteristics of 38 female longnose dace ( Rhinichthys cataractae ) from one of the southernmost populations of this species during two sampling periods in 1999 (ES=March 1999, LS=June 1999). Our data indicated that ES fish had not spawned, whereas LS fish had begun spawning. The smallest mature female captured was 56 mm SL (age 1+). Mean potential fecundity differed significantly between ES (mean±1 SD=1832±572 oocytes) and LS (mean±1 SD=775±415 oocytes) specimens. Potential fecundity was positively correlated with both standard length and somatic mass for both ES and LS specimens. Oocyte diameter frequency histograms indicated that ES specimens possessed two modes of oocytes, whereas LS fish contained two or three modes. Female longnose dace appeared to spawn more than once during a reproductive season. Oocyte number varied substantially both among individuals within periods and between periods. The number of Mode II oocytes in ES fish was positively correlated with both length and somatic mass. Female longnose dace appeared potentially capable of spawning 6+ clutches per year. GSI values for longnose dace ranged from a high of 21.4% (LS specimen) to 2.4% (ES specimen). Regression analysis demonstrated that there was no evidence of differential reproductive effort between longnose dace of different size in this population.  相似文献   

17.
Abstract –  Topeka shiners ( Notropis topeka ), an endangered minnow species, typically spawn on or around breeding Lepomis sunfish (Centrarchidae) nests. Why spawning Topeka shiners are attracted to these nests is unclear, but having the nesting sunfish provide shiner eggs with improved aeration, a lessening of siltation, and protection from egg predators are possibilities. We tested the substrate utilisation of Topeka shiners in outdoor tanks in the absence of sunfish to determine the shiner's fundamental choice. Shiners were provided with substrate patches of cleaned sand, small gravel, large gravel, and small cobble, and the bare floor of the tank. The substrate above which a male shiner established his territory was used as evidence of choice. A statistically significant choice for sand substrates was demonstrated. This fundamental choice might influence which sunfish nests Topeka shiners use, given that nest substrate characteristics differ both between sunfish species and within species by spawning site location.  相似文献   

18.
This study was conducted to determine the effects of broodstock diet on flame angelfish (Centropyge loriculus) reproduction and generate baseline spawning performance (mean fecundity, egg fertilization, egg viability) and egg biochemistry data for this species. Sixteen flame angelfish broodstock pairs were maintained on one of three formulated diets or a raw diet (consisting of squid, shrimp, fish eggs and algae) to determine the effect of diet composition on the fecundity, egg fertilization rates and egg viability over a 7‐month period. Although all the diets supported similar mean spawn frequency and fecundity over the duration of the experiment, the mean fertilization rates and egg viability were significantly greater among pairs receiving the raw diet. Egg fatty acid composition was generally reflective of the maternal diet and similar to the values reported for other tropical species. In particular, dietary factors such as n‐3 highly unsaturated fatty acid and ARA level (which were elevated in the raw diet and eggs from fish receiving that treatment) are correlated with egg quality and are therefore worthy of future investigation. Because of the ease of conditioning, adaptability to varied formulated diets and continuous, sustained reproductive output, flame angelfish are an excellent model for examining the factors affecting marine fish egg and larval quality.  相似文献   

19.
The aim of this preliminary study was to evaluate the influence of different feeding regimes on the quality of reproduction in pikeperch. Three diets were tested: forage fish (FF), a commercial dry feed (DD) and a mix of both (FD).  The diets were given to fish throughout a complete reproductive cycle. During the spawning season, couples were injected with human chorionic gonadotropin (hCG) and let to spawn on nests. Proportion of running males, spawning and hatching success and larval quality (weight, length, body protein, total lipid, fatty acid and lipid class compositions and resistances to osmotic shock and starvation stress tests at hatching) were evaluated. The proportion of running male was lower in the DD group than in the FF and FD groups (54% for DD against 76–89% for FF and FD). In addition, 25%, 62.5% and 75% of injected couples gave spawning that hatched in DD, FF and FD groups respectively. Larval quality parameters were not significantly different between treatments. The results indicate that overall quality of reproduction was higher in FF and FD treatments than in DD. It suggests that the dry feed used was not totally adequate for pikeperch reproduction. Relations between breeder reproductive performances and the feed compositions are discussed.  相似文献   

20.
Lumpfish, Cyclopterus lumpus L., has an extended ovary development period and a relatively long spawning season. It therefore seems unlikely that individuals spawning later in the season would be able to recover from spawning and develop their gonads in time to spawn during the early part of the season the following year. The hypothesis that individuals spawning early or late in a spawning season would spawn early or late the following year was tested using fish tagged in Iceland between 2008 and 2017. The tagging date and recapture date the following year were positively correlated with an average of 356 days at large (DAL). Fish sampled from the fishery indicate that tagging/recapture date gives an indication of spawning time. From this, it was concluded that spawning time in the current year can be used to predict spawning time the following year. As fishing effort was greatest at the end of April/beginning of May, it seems likely that fish that come to spawn at this time will be subject to a higher fishing mortality. Therefore, they will be less likely to spawn successfully than fish spawning earlier or later in the year. If spawning time is under genetic control, then this could have consequences for the spawning phenology of lumpfish.  相似文献   

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