Mortality Of Fish Larvae Research Articles

Momma's larvae: Maternal oceanographic experience and larval size influence early survival of rockfishes

AbstractIdentifying factors that affect larval mortality is critical for understanding the drivers of fish population dynamics. Although larval fish mortality is high, small changes in mortality rates can lead to large changes in recruitment. Recent studies suggest maternal provisioning can dramatically affect the susceptibility of larvae to starvation and predation, the major sources of early‐life mortality. We measured otolith core width‐at‐extrusion and validated that this is a proxy for larval size‐at‐extrusion for eight species of rockfishes (genus Sebastes) to examine the influence of initial larval size on larval growth and survival and to understand how oceanographic conditions experienced by gestating females affect larval size (i.e., quality). Otolith core width‐at‐extrusion was significantly positively related to larval rockfish recent growth rate (5/7 species with sufficient sample size) and survival (all eight species). This suggests that individuals that are larger at extrusion generally grow faster and are more likely to survive early life stages. Otolith core width‐at‐extrusion was positively related to higher presence of Pacific Subarctic Upper Water and was negatively related to warmer, saline waters at the depths gestating mothers inhabited during the months prior to larval collection. In addition, otolith core width was larger further from fishing ports, possibly because these locations were historically less fished, contained more older, larger females, and/or had inherently better habitat quality (higher Pacific Subarctic Upper Water) than sites closer to shore. These results indicate that the environmental conditions female rockfish experience during gestation drive the size of the larvae they produce and impact larval growth and survival.

A novel approach for estimating growth and mortality of fish larvae

Abstract Accurate estimates of growth and mortality are needed to understand drivers of production and cohort success. Existing methods for estimating mortality rates, such as catch-curves, require large sample sizes, as they work by grouping individuals into age-bins to determine a frequency distribution. Yet, sampling enough larvae is often not possible at fine scales within the constraints of research projects, due to low density of larvae in pelagic environments. Here, we develop a novel method to simultaneously estimate growth and mortality rates of fish larvae as a continuous function of size using theory of size-structured populations, eliminating the need to group data into age-bins. We compare the effectiveness of our model to existing methods by generating data from a known distribution. This comparison demonstrates that while all models recover correct parameter values under ideal circumstances, our new method performs better than existing methods when sample sizes are low. Additionally, our method can accommodate non-linear growth and mortality functions, while also allowing growth and mortality to vary as functions of environmental co-variates. This increased accuracy and flexibility of our method should improve our ability to relate variability in larval production to environmental fluctuations at finer spatial scales.

The impacts of seasonal variation on the immune status of Nile tilapia larvae and their response to different immunostimulants feed additives

Few data are available on the thermal tolerance of Nile tilapia fish larvae in relation to their immune status and survival. The aims of this work were to evaluate the immune status of one day old Nile tilapia (Oreochromis niloticus) larval stage collected at the beginning (March), middle (August) and at the end (October) of hatching season through morphometric assessment of the larvae parameters including yolk sac diameter, body length and width as well as the expression of some immune-related genes (rag, sacs and tlr), inflammatory (il1b and il8) and stress related genes (hsp27, hsp70). Also, to compare the effect of three different immunostimulants (β-glucan, Vitamin C, and methionine/lysine amino acids mix) on the expression of the studied genes at two variant temperatures (23 ± 1 °C and 30 ± 1 °C) in experimental study for 21 days. The immune status of Nile tilapia is affected by thermal fluctuation throughout the hatching season reflected by altered yolk sac size, length, and expression of the immune and stress related genes of the larvae, the best performances was observed at the beginning of the hatching season (March). High temperature (30 °C) suppress immune and stress responses throughout downregulation of all the genes under study, mask any effects for the immunostimulants, increased mortality in fish larvae suggesting narrow thermal tolerance range for the larvae compared with the adult fish.We recommend the use of amino acid mix as immunostimulant for Nile tilapia larvae, it reduces the mortality percentage and improve cellular response. Also, the use of β-glucan should be prohibited during this developmental stage of larvae, it induced the highest mortality percentage.

Influence of wind events on larval fish mortality rates in the southern California Current Ecosystem

Wind-induced mixing can affect the vertical distribution of plankton in the upper water column, influencing the prey available for larval fishes. The stable ocean hypothesis proposes that periods of calm winds facilitate the development of plankton layers at concentrations sufficient for successful larval foraging and increased survival. Conversely, storm events redistribute prey, leading to reduced foraging success. Here, we investigate this hypothesis by comparing larval fish mortality rates estimated from 37 years of ichthyoplankton data against metrics of wind events defined as storms and calm periods. Contrary to expectations, we found that mortality for Pacific hake (Merluccius productus) significantly decreased as storm events increased in the southern California Current Ecosystem. Mortality rates for northern anchovy (Engraulis mordax), Pacific sardine (Sardinops sagax), Pacific mackerel (Scomber japonicus), and jack mackerel (Trachurus symmetricus) had no relationship to storms, and no species’ mortality rates were related to the number of calm events. Our results highlight the differing sensitivities of larval survival among fishes in the region and indicate that responses to atmospheric processes are species-dependent.

Death from near and far: alternate perspectives on size-dependent mortality in larval fish

Death from near and far: alternate perspectives on size-dependent mortality in larval fish

Development of a bacterial challenge test for gnotobiotic Nile tilapia Oreochromis niloticus larvae

Gastrointestinal microbiota have an important impact on fish health and disease, stimulating interest in a better understanding of how these gastrointestinal microbial communities are composed and consequently affect host fitness. In this respect, probiotic microorganisms have been extensively used in recent aquaculture production. To study the use of probiotics in the treatment of infectious diseases, the establishment of a method of experimental infection to obtain consistent results for mortality and infection in challenge tests is important. In pathogen-screening tests, 4 candidate pathogenic bacteria strains (Edwardsiella ictaluri gly09, E. ictaluri gly10, E. tarda LMG2793 and Streptococcus agalactiae LMG15977) were individually tested on xenic Nile tilapia larvae. Only Edwardsiella strains delivered via Artemia nauplii, with or without additional pathogen delivery via the culture water, led to increased mortality in fish larvae. A gnotobiotic Nile tilapia larvae model system was developed to provide a research tool to investigate the effects and modes-of-action of probiotics under controlled conditions. A double disinfection procedure using hydrogen peroxide and sodium hypochlorite solution was applied to the fish eggs, which were subsequently incubated in a cocktail of antibiotic and antifungal agents. In the gnotobiotic challenge test, E. ictaluri gly09R was added to the model system via Artemia nauplii and culture water, resulting in a significant mortality of the gnotobiotic fish larvae. The developed gnotobiotic Nile tilapia model can be used as a tool to extend understanding of the mechanisms involved in host-microbe interactions and to evaluate new methods of disease control.

Limited contribution of predation by zooplanktivorous cyprinids to 0+ fish mortality

Summary Predation by zooplanktivorous cyprinids was hypothesized as substantially contributing to larval fish mortality. To test this assumption, potential predators were sampled by electric fishing at sites and times of high fish larvae densities in the lower Oder River, Germany, in 2002 and 2003. At ten sites with high prey fish densities, all fishes ≥1+ and 0+ pike – all considered potentially predating on fish larvae – were captured, anaesthetised, and fixed. In the laboratory, 982 guts, respectively, stomachs were dissected and checked for fish larvae and larvae remains. Predation on 0+ fish was detected in the primary piscivorous fishes Esox lucius L. and Aspius aspius (L.), and facultative piscivorous Perca fluviatilis L., whilst none of the other nine species examined consumed fish. These findings implicate that predation by planktivorous cyprinids did not explain the typically strong decline in larval fish densities in the first weeks after hatching.

Relationship between oxygen consumption, growth and survival of larval fish

This work aimed to evaluate the relationship between morphological development, oxygen consumption and reduced mortality in larval fish. We measured the resting metabolic rate (RM), specific metabolic rate (SMR) and the change in the total length during the larval stage of four fish species. Resting metabolism decreased from hatching to mouth opening, and then increased after mouth opening. The changes in the SMR were variable during the larval stage. After hatching, there was no increase in SMR in yolk-sac larvae. However, SMR increased between mouth opening and the onset of notochord flexion and then decreased during notochord flexion before finally stabilizing. We observed two peaks in mortality during the larval period of all species: between mouth opening to the onset of notochord flexion and from the completion of notochord flexion to the juvenile stage based on the per cent mortality and the number of dead fish collected from the bottom of the rearing tank. Interestingly, the changes in SMR coincided with these periods of mortality. We hypothesize that larvae require more energy during these periods of larval development and are thus more susceptible to mortality when energy is insufficient. Thus, it is important to supply enough nutrition to larvae in during early development to prevent mass larval mortality.

Influence of copper exposure on whole‐body sodium levels in larval fathead minnows (Pimephales promelas)

Because metals such as Cu inhibit ionoregulation, the increased energy requirement to counter passive diffusive losses in soft water may translate into increased sensitivity to metal exposure. We developed a method to determine whole-body Na concentrations of larval fathead minnows (Pimephales promelas) as a physiological indicator of health. This method was used to characterize net rates of Na flux from fish exposed to Cu in the presence of varying levels of hardness and alkalinity. In extremely soft waters (hardness, < or = 10 mg/L as CaCO(3)), larval fish experienced rates of net whole-body Na loss greater than what has been observed in juvenile and adult fish when exposed to Cu at concentrations near the median lethal concentration. Elevating hardness (>10 mg/L as CaCO(3)), however, decreased the apparent kinetics of Na loss caused by Cu exposure, which suggests the process was related to uncompetitive inhibition of Cu by hardness cations. Although the percentage of Na loss associated with mortality in larval fish was similar to that in juvenile and adult fish (30% loss of exchangeable Na pool), larvae reached this level within 12 h of exposure, and it was not representative of the onset of mortality. These results suggested that ionoregulatory measures by themselves are not a conclusive metric for Cu regulation using larval fish. To account for increased sensitivity in low-hardness waters in the development of biotic ligand models, the critical amount of Cu associated with the gill to cause mortality (i.e., the median lethal accumulation value) should be characterized more appropriately as a function of hardness below 20 mg/L as CaCO(3).

Association between bacterial community structures and mortality of fish larvae in intensive rearing systems

Bacterial community structures were analyzed in water used for rearing fish larvae by fluorescence in situ hybridization. In Experiment 1, red sea bream Pagrus major larvae were reared in two commercial seed production tanks. The survival rate in Tank 1 was higher than in Tank 2, even though phytoplankton, Nannochloropsis sp., was added to both tanks. In Tank 2, γ-proteobacteria became dominant (∼70% of total bacteria) on day 13, there after heavy larval mortalities occurred. In Tank 1, however, α-proteobacteria and the Cytophaga-Flavobacterium cluster were predominant from day − 1 until day 13; no significant mortality was recorded. In Experiment 2, marble goby Oxyeleotris marmoratus larvae were cultured with or without Nannochloropsis sp. At the end of the experiment, larval survival rates in aquaria with Nannochloropsis sp. were significantly (P <0.05) higher than those without. In rearing water without Nannochloropsis sp., γ-proteobacteria increased during rearing. In rearing water with Nannochloropsis sp., α-prote obacteria and the Cytophaga-Flavobacterium cluster were predominant at the beginning of the experiments and the relative abundance of γ-proteobacteria was maintained at a lower level throughout the experiments. The predominance of α-proteobacteria and the Cytophaga-Flavobacterium cluster appears to be a good indicator of successful larval production.

Growth and nutritional condition of the larvae of Odontesthes microlepidotus (Atherinidae): an experimental approach

The relation between the feeding and mortality of fish larvae is mediated not only by starvation but also by their growth. In this work, daily otolith ring deposition was analysed in laboratory-reared larvae of Odontesthes microlepidotus (Jenyns), and their growth was studied in relation to ring number and otolith diameter. The nutritional condition of these larvae was assessed by means of morphometric comparisons between fed and starved larvae in order to develop a tool to evaluate the nutritional status of larvae in breeding areas. Changes in body shape have been found as a consequence of starvation. No dependence was found between mean hepatocyte nuclear area and fasting.

Predation on Herring Larvae and Eggs by Sand-Eels Ammodytes Marinus (Rait) and HyperoplusLanceolatus (Lesauvage)

Many field observations have been made on predation by a variety of fish species on the demersally spawned eggs of the Atlantic herring (Clupea harengus L.) (Dunn, 1898; Bowman, 1922; Hempel &amp; Hempel, 1971; Toresen, 1985). Field observations on the predation of herring larvae by fish are comparatively rare although jellyfish medusae have been identified as larval predators (Van der Veer et al, 1983; Moller, 1984). Recently several experiments have been carried out on the predation of medusae and other planktonic organisms (Bailey &amp; Batty, 1983) and of fish on herring larvae (Christensen, 1983; Fuiman &amp; Gamble, 1987). Despite the lack of field observations Hunter (1984) considered that predation, most probably by fish, was the major cause of mortality in fish larvae.

Influence of Alternative Prey Abundance on Pelagic Fish Predation of Larval Fish: A Model

In this model of predation on larval fish by pelagic fish, I postulate that variations in the abundance of the more numerous alternative prey population can determine the time required by a predator to attain its maximum ration. The model predicts that larval fish mortality should be a direct function of the abundance of their predator scaled relative to alternative prey abundance. A test of the model using data from the California Current reveals that mortality of larval northern anchovy (Engraulis mordax) shows a significant relationship with the predator-to-prey ratio (pelagic fish biomass/Zooplankton biomass). Other possible interpretations of this result and problems of model parameterization are discussed.

Methods of Estimating Larval Fish Mortality from Daily Increments in Otoliths

Two methods are presented for estimating instantaneous daily mortality rates of larval fishes with otolith-increment data. The first involves construction of a histogram of the numbers of daily increments per larva from a sample of larvae, and estimation of mortality from the decline in the loge-transformed increment-frequency curve. The second approach is to convert larva lengths to number of increments with a growth curve derived from otolith data, and then to estimate mortality from the descending limb of a loge-transformed increment-frequency histogram. Counts of daily increments in otoliths of larval anadromous alewives Alosa pseudoharengus collected from a coastal Massachusetts pond were used to compare results from these two methods with results from a third method that uses the decline in catch per unit effort of larvae through time. The estimate of instantaneous daily mortality for larval alewives from otolith methods was 0.122, which was an average rate for larvae 6.0 to 13.9 mm total length over a 1-month sampling period. The three methods generally produced similar mortality estimates over large sampling periods; however, otolith-derived mortality estimates from single sampling dates were highly variable. Major advantages of otolith increment methods over traditional catch-curve methods for estimating larva mortality are elimination of the need for fitting a growth curve to estimate mortality and the ability to obtain better estimates of mortality for individual cohorts of larvae.

Preliminary results on the nutritional evaluation of ω3-HUFA-enriched Artemia nauplii for larvae of the sea bass, Dicentrarchus labrax

Freshly hatched San Pablo Bay and Great Salt Lake Artemia nauplii (ω3-HUFA-poor) and enriched meta-nauplii (ω3-HUFA-enriched) were compared to Reference Artemia nauplii (ω3-HUFA-rich) as a food source for the larvae of the sea bass, Dicentrarchus labrax. Significant differences in survival and biomass production between the treatments could be attributed to the ω3-HUFA content of the food. A delayed mortality in fish larvae fed the Great Salt Lake Artemia is suspected to be caused by a high level of α-BHC in this Artemia source. Growth was not significantly different between the treatments, most probably due to the large variation in growth rate within the treatments, as well as the low number of surviving fish in some treatments.

Opportunistic Cyclopoid Prédation on Fish Larvae

Exceptional spring spawning of yellow perch (Perca flavescens) in an inland coastal lake resulted in very high larval fish densities (up to 41 900/1000 m3) and facultative predation by adult female Diacyclops thomasi on newly hatched larvae (maximum predation density: 8740/1000 m3), as evidenced by cyclopoid attachment to fish larvae in field collections. This predation suggests that larval fish mortality and possibly cyclopoid population growth are affected. Opportunistic cyclopoid predation on fish larvae may also alter zooplankton community structure by changing the feeding pattern of cyclopoids. Lack of significant predation on other species of fish larvae is probably due to temporal and spatial asynchrony of predator and prey, low probability of encounter, robust nature of certain fish species, and effective swimming and escape ability.

RNA-DNA ratio: an index of larval fish growth in the sea

Data on water temperature, RNA-DNA ratio, and growth of eight species of temperate marine fish larvae reared in the laboratory were fit to the equation: $$G_{pi} = 0.93{\text{ }}\operatorname{T} + 4.75{\text{ RNA - DNA}} - 18.18$$ where Gpi is the protein growth rate in % d-1 and T is the water temperature. Water temperature and larval RNA-DNA ratio explained 92% of the variability in growth rate of laboratory-reared larvae. The model is useful over the entire range of feeding levels (starvation to excess), temperatures (2° to 20°C) and fish species studied. Estimates of recent growth of larval cod, haddock, and sand lance caught at sea based on water temperature and RNA-DNA ratio ranged from negative to 26% d-1. These data demonstrate the importance of food availability in larval fish mortality and suggest that short-term growth under favorable conditions may be considerably higher than expected from long-term indicators. RNA-DNA ratio analysis offers new possibilities for understanding larval growth and mortality, and their relation to environmental variability.

Larval fish assemblages and associations in the north-east Pacific Ocean along the Oregon coast, winter-spring 1972–1975

Consistent patterns of larval fish distributions were found to occur along the Oregon coast between the Columbia River and Cape Blanco during winter-spring months for the years 1972–1975. Six data sets from March 1972, April 1972, March 1973, April 1973, March 1974 and March 1975 were analyzed using the pattern recognition techniques of numerical classification. Data included 306 bongo net samples containing 34 029 larval fish in 93 taxa. Coastal, transitional, and offshore assemblages (station groups) were present in each of the sampling periods. The region of transition from coastal to offshore assemblages roughly paralleled the shelf-slope break. Coastal and offshore species associations (species groups) were also always present. Species in the coastal and offshore groups never co-occurred. The consistency of these patterns is probably related to the spawning location of adults and to the predominate longshore coastal circulation patterns. Differences in the extent of offshore distribution of the coastal assemblages among years reflected differences in local coastal wind patterns. Differences in the dominant taxa and their relative abundances within assemblages may reflect variation in timing of spawning and survival of larvae in the planktonic phase. Despite the differences, the persistent occurrence of three major assemblages, coastal, transitional and offshore, and three major species groups from year to year supports the idea that these patterns of larval fish distributions are constant features over the continental shelf region off Oregon. The constancy of these patterns over four years suggests that transport may not be a major cause of larval fish mortality and recruitment failure in this region.

Efficiency of Nets and a New Device for Sampling Living Fish Larvae

Mortality of fish larvae when collected with a plankton net was shown to increase with the velocity of water moving through the net. In addition, the net retained fewer larvae at higher velocities. A device was designed and tested which efficiently concentrated living fish larvae at low velocities and reduces collection mortality. Key words: fish larvae mortality, plankton nets, new sampler.

LARVAL FISH MORTALITY

School Science and MathematicsVolume 71, Issue 2 p. 182-182 LARVAL FISH MORTALITY First published: February 1971 https://doi.org/10.1111/j.1949-8594.1971.tb11493.xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume71, Issue2February 1971Pages 182-182 RelatedInformation