Post-spawning Survival Research Articles

Administration of Arginine Vasotocin and modified Isotocin improve artificial propagation and post-spawning survival of female yellow catfish

Low rate of spawning and high percentage of death after artificial propagation are frequently observed in catfish, which do harms to the long-term population stability and genetic breeding programs in aquaculture. In this study, yellow catfish (Pelteobagrus fulvidraco), an important freshwater species in China was used as a research model, since the farmed female yellow catfish had poor reproduction performance and a high death rate after treatment with the traditional exogenous hormones, luteinizing hormone releasing hormone analogues2 (LHRH-A2) and human chorionic gonadotropin (HCG). We tried to investigate the roles of the Arginine Vasotocin (AVT)/ Isotocin (IT) neuropeptide family in reproduction and design an optimal strategy for inducing artificial propagation in yellow catfish. Two copies of pro-avt and pro-it were detected in hypothalamus and ovaries of yellow catfish, and their mRNA levels gradually increased during spring-summer season. Furthermore, the transcript levels of pro-avt and pro-it in hypothalamus significantly increased after injection of LHRH-A2 and HCG. Although AVT could not induce germinal vesicle breakdown (GVBD) in female yellow catfish, administration of AVT significantly stimulated premature ovulation in a dose-dependent manner and induced the expression of ovulation-related genes, ptgs2a and acvr1. Furthermore, there is a significant up-regulation of serum prostaglandin E2 (PGE2) and luteinizing hormone (LH) in female fish after AVT treatment, whereas no difference was observed in follicle stimulating hormone (FSH). Since IT of yellow catfish was insoluble in saline, a rigid peptide segment was added at the end of IT (the modified IT was named IT-M), which could greatly improve its solubility and induce ovulation in female yellow catfish. Subsequently, we demonstrated that adding carp pituitary extraction (CPE) to the second injection of traditional methods could efficiently improve the spawned fish, eggs production, fertilization rate, hatching rate and post-spawning survival of female yellow catfish, despite at a relatively high cost in hormones. We further discovered that IT-M + AVT could substitute for HCG + CPE in the second injection and had high efficiency in artificial propagation, reducing the hormone costs to less than one-third. Altogether, we provide an effective and affordable combination of exogenous hormones to improve reproduction performances and post-spawning survival rate in yellow catfish.

Local variation in the timing of reproduction and recruitment in a widely distributed diadromous fish

ABSTRACT Īnanga (Galaxias maculatus) is a widespread freshwater fish, found around coastal New Zealand, Chatham Islands, southern Australia and southern South America, exhibiting both diadromous and land-locked life history patterns. We assessed population size structure, size at maturity, timing of reproduction, and post-reproductive survival in the Waikouaiti and Kakanui rivers, two regionally important G. maculatus populations in southern New Zealand. Size at maturity varied between rivers and sexes, with males generally maturing at smaller sizes than females. The timing of reproduction and recruitment was observed to vary across a relatively small spatial scale. Population length-frequencies indicated that both populations exhibited annual population dynamics, with most individuals spawning in their first year, then apparently dying soon afterwards (as indicated by a marked drop in post-spawning abundance). However, a few individuals with recently spent or resting gonads were present over the winter months, indicating some post-spawning survival. There was a lower frequency of exceptionally large (putatively 1+) individuals than reported for other populations around New Zealand and elsewhere, suggesting over-winter survival following spawning varies. Based on the variation in life history characters over small spatial scales, we suggest that management of regionally important G. maculatus populations should be based on catchment level information.

Can Energy Depletion of Wild Atlantic Salmon Kelts Negotiating Hydropower Facilities Lead to Reduced Survival?

Repeat spawners constitute an important component of Atlantic salmon populations, but survival of post-spawning individuals (kelts) are often compromised by anthropogenic structures such as hydropower plants (HPPs). Potential effects of HPPs include migration delays and associated increased energy depletion, which potentially results in increased overall mortality. We combined a detailed 3D hydraulic model with high-resolution 3D tracking of tagged kelts (length 73–104 cm) to obtain estimates of kelt movement through water. These estimates were then used in an energetics model to estimate hourly energy expenditure while negotiating the HPP area. Hourly kelt energy expenditure varied between 0.8 and 10.1 kJ × h−1 and was dependent on kelt length. Degree of additional energy depletion can amount to several percent of remaining energy content (our study indicates 4–5 percentage points) potentially leading to reduced post-spawning survival. In turn, this can nullify the iteroparous breeding strategy and jeopardize long-term stability and persistence of Atlantic salmon populations inhabiting HPP rivers.

Synergistic Combination of Exogenous Hormones to Improve the Spawning and Post-spawning Survival of Female Yellow Catfish.

Multiple repeat spawners make large contributions to long-term population stability and aquaculture breeding programs. A high percentage of female yellow catfish (Pelteobagrus fulvidraco) died for spawning failure or incomplete spawning after artificial spawning by traditional synthetic hormones including human chorionic gonadotropin (hCG), luteinizing hormone releasing hormone (LHRH), and domperidone (DOM). The present study was designed to compare the efficacy of different combinations of exogenous hormones for inducing ovulation in yellow catfish using hCG, LHRH, DOM, and carp pituitary extraction (CPE). We found a optimal strategy for exogenous hormones administration, the mixture of LHRH/CPE for the first injection and LHRH/CPE/DOM for the second injection, could greatly improve the rates of spawning success, weight of ovulated eggs and survival rate after spawning. Interestingly, a population of female yellow catfish with defective reproductive duct could not spawn and showed high mortality after induced by a combination of hCG/LHRH/DOM, whereas a synergistic combination of hCG, LHRH, DOM, and CPE could efficiently induce spawning and reduce mortality in the defective yellow catfish, in which a significant decrease of Vitellin and E2 levels. Altogether, our findings provide an effective combination of exogenous hormones to improve spawning and post-spawning survival of female yellow catfish.

Condition-dependent skipped spawning in anadromous brown trout (Salmo trutta)

Repeat spawners of anadromous salmonids may contribute significantly to population resilience by providing multiple cohorts to both seawater and freshwater life stages. In this study, winter survival of sea trout (Salmo trutta Linnaeus, 1758) post spawners (kelts) was 89%. Sea survival increased linearly with female length with a return probability between 30% and 50%, whereas males attained a maximum return probability of 60% at 520 mm. Of the returning sea trout, 40% skipped spawning and they had significantly lower condition factor as kelts compared with those who returned after one summer. These results suggest that sex-specific differences in individual post-spawning growth–survival trade-off exist and that energetic status of descending kelts may influence the probability to skip spawning. We discuss to what extent hydropower may reduce post-spawning survival due to blocking of river descent opportunities, potentially altering the fitness landscape and favouring new life-history adaptations. From a management perspective, it is concluded that it is crucial to maintain connectivity in regulated rivers, allowing fish to complete repetitive spawning and feeding migrations, thus contributing to population productivity.

Egg cannibalism in capelin Mallotus villosus at beach and deep-water spawning habitats in the north-west Atlantic Ocean.

We investigated egg cannibalism in spawning capelin Mallotus villosus on the north-east Newfoundland coast during July 2012-2014, specifically whether sex, spawning condition (i.e., spawning or spent) and spawning habitat influenced egg cannibalism. Capelin spawning in deep-water were 4.5-14 times more likely to be cannibals than those at the beach, probably due to the higher spatial overlap of spawners and conspecific eggs within this habitat relative to beaches. Males were 2.1-3.7 times more likely to be cannibals than females, but female cannibals had more eggs per stomach. Spawning fish were 1.6-1.9 times more likely to be cannibals than spent fish, but spent female cannibals had more eggs per stomach relative to spawning males and females in either habitat. Findings suggest that cannibalism may be an important foraging strategy, especially at deep-water spawning habitat, possibly extending the spawning season for males or increasing the probability of post-spawning survival for females. Although 44% of sampled females and 50% of males were cannibals, the estimated mortality due to egg cannibalism was low (0.49-2.97% of eggs produced annually), suggesting that egg cannibalism does not influence recruitment to a great extent in Newfoundland capelin.

Evidence of iteroparity in the widely distributed diadromous fish inanga Galaxias maculatus and potential implications for reproductive output.

Gaps in understanding variability among populations of inanga Galaxias maculatus in the timing of reproduction were addressed in southern New Zealand (NZ), where G. maculatus constitutes a declining fishery. Reproductive activity was delayed by 1 month on the west coast compared with the east coast and the west coast spawning season was prolonged into winter. The evidence for post-spawning survival of some fish was unequivocal from histological studies. These older and larger fish contributed disproportionately to egg production. Estimates of fecundity were considerably lower than those previously calculated for NZ populations. The importance of quality habitats being available during critical life history periods are highlighted. It was apparent that some streams supported fish that were larger and in better condition and that this translated into greatly increased fecundity. Future research should focus on whether this is a legacy of these fish experiencing better pre-settlement marine habitat as larvae, or higher quality instream habitat enhancing the growth and development of adults.

Physiological comparisons of steelhead kelts emigrating from the Situk River, AK and Clearwater River, ID

The physiological status of migrating steelhead kelts (Oncorhynchus mykiss) from the Situk River, Alaska, and two tributaries of the Clearwater River, Idaho, was evaluated to explore potential differences in post-spawning survival related to energy reserves. Blood plasma samples were analyzed for metrics related to nutritional and osmotic status, and samples of white muscle tissue collected from recent mortalities at weirs were analyzed for proximate constituents. Female kelts from the Situk River had significantly higher plasma cholesterol, triglycerides, glucose and calcium concentrations, all of which suggested higher lipid and energy stores. Additional support for energy limitation in kelts was provided by evaluating the presence of detectable proteins in the plasma. Most all kelts sampled from the Situk River populations had detectable plasma proteins, in contrast to kelts sampled from the Clearwater River tributary populations where 27 % of kelts from one tributary, and 68 % of the second tributary were below the limits of detection. We found proximate constituents of kelt mortalities were similar between the Situk and Clearwater River populations, and the lipid fraction of white muscle averaged 0.1 and 0.2 %. Our findings lend support to the hypothesis that energetic limitations likely affect post-spawn survival in the Clearwater River kelts.

Observations of growth and postspawning survival of lumpfish Cyclopterus lumpus from mark-recapture studies.

Growth and postspawning survival of lumpfish Cyclopterus lumpus are described by mark-recapture experiments using juveniles in offshore areas in the north-east Atlantic Ocean and spawning adults in coastal Norway and Iceland. A female fish tagged as a juvenile and recaptured as an adult matured in a period of 18 months, providing the first observation on development in a wild C. lumpus. The von Bertalanffy growth function, fitted to data from recaptured fish, was used to estimate K and L∞ and recaptured fish spawning after a year at liberty indicated a postspawning survival of c. 10% in Iceland.

Metabolic adaptations of oxidative muscle during spawning migration in the Atlantic salmon Salmo salar L.

The adaptability/plasticity of the highly oxidative red muscle in Atlantic salmon was demonstrated during spawning migration. Substrate concentrations and the enzymatic pathways of ATP production were examined in red muscle obtained from Atlantic salmon at different sites along their migratory route in the Exploits River, Newfoundland, Canada. Individuals were chronologically sampled from a seawater site, two sites upstream, and at spawning. The 20% decrease in salmon body weight during the later stages of migration was accompanied by large decreases (mg dry weight(-1)) in both glycogen (P < 0.01) and total muscle lipid (P < 0.01). In contrast, water content and protein concentration (mg dry weight(-1)) of the red muscle increased by 25 and 34%, respectively, at spawning. Enzymes of the glycolytic pathways demonstrated a significant (P < 0.001) decrease in maximal activity as migration proceeded whereas enzymes of the oxidative phosphorylation pathways, specifically the citric acid cycle enzymes, exhibited an increase (P < 0.001) in maximal activity at spawning. The antioxidant enzyme superoxide dismutase also demonstrated an increase (P < 0.001) in maximal activity during the latter stages of migration. These adaptations imply that the red epaxial muscle of Atlantic salmon has a more efficient means of oxidizing lipids, while minimizing free radical damage, during the later stages of migration and spawning, thereby potentially increasing post spawning survival.

Facultative semelparity in capelin Mallotus villosus (Osmeridae)-an experimental test of a life history phenomenon in a sub-arctic fish

Two alternative reproductive modes are present in fishes and reflect the age-specific mortality encountered through ontogenesis. Life-history hypotheses suggest that semelparity (i.e. death after a single reproductive event) evolves when the ratio of juvenile to adult survival is relatively high. Conversely, a relatively low ratio of juvenile to adult survival will favour iteroparity (i.e. death after two or more reproductive events). Fisheries management associates capelin ( Mallotus villosus) spawning with mass mortality and semelparity even though life history models developed for this species suggest that females may follow an iteroparous trajectory. Capelin may spawn either inter-tidally on the beach or offshore in deeper, ocean waters but post-spawning survival and potential iteroparity has been notoriously difficult to assess in natural populations. Through a series of aquarium experiments we tested post-spawning survivability in a beach spawning and an ocean spawning population. The findings demonstrate that capelin which spawn offshore are absolute semelparous (death of both genders) while beach spawning capelin are iteroparous irrespective of sex. Beach spawning capelin regenerated ripe gonads from one spawning season to the next and provides the first conclusive evidence that capelin is physiologically capable of an iteroparous reproductive mode. The potential physical and biological processes which generate certain reproductive patterns in capelin are summarized and discussed in relation to life history hypotheses. We suggest that capelin is a facultative semelparous species in which dynamic changes within the semelparity-iteroparity continuum may occur as a result of subtle interactions between the spawning habitat, physical forcing, and predatory pressure.

Intra‐population variation in anadromy and reproductive life span in rainbow trout introduced in the Santa Cruz River, Argentina

Scale patterns, maturational status and otolith microchemistry (strontium to calcium ratios) were analysed in sympatric anadromous and non‐anadromous rainbow trout Oncorhynchus mykiss in the Santa Cruz River (Patagonia, Argentina) to investigate the life‐history differences of anadromous and non‐anadromous lifestyles and the association between maternal origin and progeny life history. The analyses revealed that both forms can give rise to one another, indicating a single population with alternative phenotypes. Anadromous fish smolted at ages 2 and 3 years, matured after 1 to 2 years in the ocean, and survived up to 11 years, spawning up to eight times. Non‐anadromous fish survived up to 6 years, spawning up to three times. The extended reproductive life span associated with anadromy in this river suggests that increased energetic and physiological demands associated with ocean migration may not necessarily result in reduced postspawning survival, as has been suggested for salmonids in general. Alternatively, reduction in parity may be regarded as the evolutionary outcome of reproductive traits resulting from the adoption of anadromy (i.e. augmented reproductive investment) coupled with long‐range migrations to and from the ocean. The life‐history patterns of Santa Cruz River rainbow trout provide a natural experiment for investigating the evolutionary transition and maintenance of anadromy and non‐anadromy within salmonid populations.

The impact of cold water releases on the critical period of post-spawning survival and its implications for Murray cod (Maccullochella peelii peelii): a case study of the Mitta Mitta River, southeastern Australia

The effects of cold water releases, as a by-product of storing irrigation water in large dams, has been a source of great concern for its impact on native freshwater fish for some time. The Mitta Mitta River, northeast Victoria, is impacted by altered thermal regimes downstream of the fourth largest dam in Australia, Dartmouth dam, with some daily temperatures 10–12°C below normal. Murray cod (Maccullochella peelii peelii) were endemic to the Mitta Mitta River; however, resident Murray cod have not been found in this river since 1992. The response of eggs and hatched larvae from Murray cod to different temperature gradients of water were measured and the post-spawning survival recorded. As a case study, post-spawning survival was then inferred from flow data for each year of operation of Dartmouth Dam, recorded since first operation in 1978, and included in a stochastic population model to explore the impact of the altered (historical) thermal regime on population viability. Experimental results revealed no egg and larval survival below 13°C and predicted historical temperature regimes point to more than 15 years of low temperatures in the Mitta Mitta River. Population modelling indicates that the impact of cold water releases on post-spawning survival is a significant threatening process to the viability of a Murray cod population. Additionally, we consider changes to the thermal regime to explore how the thermal impact of large dams may be minimized on downstream fish populations through incrementally increasing the temperature of the releases. The modelled Murray cod population responds to minor increases in the thermal regime; however, threats are not completely removed until an increase of at least 5–6°C. Copyright © 2005 John Wiley & Sons, Ltd.

Direct assessment of post-spawning survival of female capelin, Mallotus villosus

Assessment of spawning survival for female capelin Mallotus villosus (Pisces: Osmeriformes) greater than 12 cm in length was made in the autumn of 1995–1997 comparing a histological technique with existing methods. An intensive macroscopic visual assessment of selected samples from 1995, 1996 and 1997 revealed that 10, 20 and 40% of the females were recovering from spawning respectively each year. Histological assessments of the same fish revealed that 20% in 1995, and nearly 60% of the fish in 1996 and 1997 showed physiological evidence of previous spawning. The proportion of recovering spawners increased with both length and age of the fish. One sample from the Northwest Atlantic Fisheries Organization area of 2J during October 1997 contained nearly 90% recovering fish. The potential impact of the fishery in light of the variability in post-spawning survival of the iteroparous female capelin is discussed.

Hyperadrenocorticism in spawning migratory and nonmigratory rainbow trout ( Salmo gairdnerii); Comparison with pacific salmon (genus Oncorhynchus)

A comparative study was made of the physiological and histological changes associated with sexual maturation and spawning in migratory (anadromous) and nonmigratory (lacustrine) rainbow trout. These changes in migratory trout (steel-head); hyperplasia of the adrenocortical tissue, elevated concentrations of 17-hydroxycorticosteroids (17-OHCS), hyperglycemia, depletion of lymphocytes from spleen and thymus, hypertrophy of the islets of langerhans, and degeneration of many of the internal organs, are characteristic of hyperadrenocorticism. Whereas the nonmigratory trout showed adrenal hyperplasia, 17-OHCS concentrations, and lymphocyte depletion as marked as in steelhead, hyperglycemia was absent and degenerative changes in the internal organs were slight. Comparison with similar physiological and histological alterations in Pacific salmon brought out the fact that the salmon, all of which die after spawning, show more pronounced changes than do the steelhead trout which suffer only a partial post-spawning mortality. The nonmigratory trout usually survive their first reproduction. Differences in food intake during sexual development in these three salmonids; complete starvation in salmon, limited and irregular feeding in steelhead, continued active alimentation in nonmigratory rainbow trout, are discussed, and their possible relationship to the catabolic effect of 17-OHCS and to post-spawning survival, is indicated.