Distribution Of Larvae Research Articles

Physical-biological interactions in the ocean: case studies from the northern Canary Current Upwelling Ecosystem

Physical-biological interactions in the ocean: case studies from the northern Canary Current Upwelling Ecosystem

Composition and distribution of Serranidae (Actinopterygii:Perciformes) larvae in the Southeastern Brazilian Bight

This study describes the taxonomic composition and horizontal distribution of Serranidae larvae along the Southeastern Brazilian Bight (SBB, approximately 22°S and 28°S), and investigates how environmental and biological factors influence the larval distribution. Ichthyoplankton samples were collected in 10 oceanographic cruises conducted from 1975 to 1981. Serranidae larvae were identified into 15 species, including 11 genera and four subfamilies. Except for Diplectrum formosum, which was widely distributed throughout the SBB, Hyporthodus spp. and Baldwinella vivanus were distributed in the southern portion of the SBB, while other species were distributed mainly in the northern portion of the SBB, inside the 200 m isobath. Local depth, latitude, distance from the closest island and salinity were factors that influenced significantly on the distribution and abundance of the most abundant taxa D. formosum, Diplectrum spp., Serranus spp. and Mycteroperca spp. Significant progress was made in identifying grouper larvae from the SBB (Epinephelus morio, Epinephelus itajara and Hyporthodus nigritus).

Fish larvae distribution among different habitats in coastal East Africa.

Fish larvae abundances, diversity and trophic position across shallow seagrass, coral reef and open water habitats were examined to characterize their distribution in coastal East Africa. Larvae were identified to family and analysed for abundance differences between sites and habitats, trophic level using stable-isotope analysis and parental spawning mode. Abundances differed greatly between sites with the highest numbers of larvae occurring in the open-water and seagrass habitats. Larval fish diversity was high across habitats with 51 families identified with small differences between sites and among habitats. Notably, larvae of abundant large herbivorous fishes present in reef and seagrass habitats were almost completely absent at all sampling locations. In the seagrass, demersal spawned larvae were more abundant compared with the reef and open-water habitats. Stable-isotope analysis revealed that fish larvae have a varied diet, occupying trophic level two to three and utilizing planktonic prey. This study offers new insights into distributional aspects of fish larvae along the East African coast where such information is sparse.

Microplastic contamination in an urban estuary: Abundance and distribution of microplastics and fish larvae in the Douro estuary

Estuaries are productive environments used by many fish as nursery grounds. The initial stages of fishes are highly vulnerable to (a)biotic factors, and anthropogenic pressures, influencing fish larvae assemblages along the estuary. Microplastics (MPs < 5 mm) are particularly dangerous to early life stages of fishes because their ingestion can induce gut blockage, limiting food intake or exposing organisms to contamination due to MPs capacity to absorb pollutants. Present work aimed to investigate the contamination of an urban impacted estuary (Douro estuary, NW Portugal) by MPs, and study the abundance and distribution of MPs and fish larvae in this estuary. Monthly sampling surveys were performed from December 2016 to December 2017, in nine stations along the estuary. Sub-surface planktonic horizontal trawls were performed to collect fish larvae and MPs. Planktonic samples were sorted, and fish larvae identified. MPs density was determined using a protocol optimized in our laboratory. A total of 1498 fish larvae belonging to 32 taxa were collected, with a mean density of 11.66 fish larvae 100 m−3. During the spring-summer period, it was observed the typical increase in the density and diversity of the larval assemblage. Diversity was generally low, with the high dominance of very few taxa, namely the common goby, Pomatoschistus microps. Different types of MPs were found, namely fibers, soft/hard plastic, colorful/transparent plastic, in a total of 2152 particles, with a mean density of 17.06 MPs 100 m−3. Hard MPs and fibers were the most predominant types, representing 83% of the total MPs collected. In some months the number of MPs surpassed the number of fish larvae, with an average ratio of 1.0 fish larvae:1.5 MPs. Such results are concerning, highlighting that a higher availability of MPs may facilitate their ingestion by fish and therefore increase possible impacts in these communities.

Aedes albopictus (Diptera: Culicidae) on an Invasive Edge: Abundance, Spatial Distribution, and Habitat Usage of Larvae and Pupae Across Urban and Socioeconomic Environmental Gradients.

The Asian tiger mosquito [Aedes albopictus (Skuse)] is an invasive species of public health importance that is currently expanding its range in the Northeast United States. Effective Ae. albopictus control depends on a thorough understanding of factors influencing their abundance, spatial distribution, and habitat preference. We conducted a series of container surveys for Ae. albopictus larvae/pupae over 2 yr across nine sites in neighborhoods along its invasive range in southern New York. Selected sites represented a gradient of percent impervious surface and median household income. Two hypotheses were tested: 1) Ae. albopictus larval/pupal abundance increases and spatial distribution becomes less clustered as site-level median income decreases and percent impervious surface increases because of increased larval habitat quality and availability; and 2) container-level characteristics are predictive of Ae. albopictus larval/pupal infestation across a range of sites. In 2016, neither median household income nor impervious surface predicted Ae. albopictus abundance. In 2017, sites with greater impervious surface were more heavily infested by some measures. In both years, Ae. albopictus larval/pupal spatial distribution as measured by K-function was more clustered in with greater median household income. Most container characteristics were either not predictive of Ae. albopictus or varied between years. Based on the variability of predictive container characteristics, we conclude that identification of key containers is not useful in this region. However, Ae. albopictus can be nonhomogenously distributed or abundant based on income level and impervious surface. Improved control of immatures should consider these regional predictors of Ae. albopictus populations.

Determining Frankliniella fusca (Thysanoptera: Thripidae) Egg Distribution in Neonicotinoid Seed-Treated Cotton.

Frankliniella fusca (Hinds) (Thysanoptera: Thripidae) is an early-season cotton pest. Seedlings are injured by larvae, which hatch from eggs oviposited into seedlings and feed on developing plant tissue. Better understanding F. fusca oviposition in cotton may improve their management and address new challenges such as resistance to neonicotinoid seed treatments (NSTs). Cotton seedlings exposed to F. fusca were either cleared and stained to determine egg density and location, or dissected and washed to determine larval distribution. Experiments were conducted in the greenhouse with a susceptible population and field with a NST-resistant population. Eggs of both populations were recovered predominantly in cotyledons. Larvae were more uniformly distributed on seedlings. On NST seedlings, oviposition by the susceptible population was reduced and preference shifted to true leaves. NSTs did not alter egg placement by the resistant population. These findings suggest that injury to cotton seedlings is primarily caused by F. fusca emerging on the cotyledons, and then moving to developing leaves. The oviposition shift in NST plants correlates with how systemic NSTs have been reported to concentrate in cotyledons. This can better inform management tactics in cotton, such as well-timed foliar sprays, which, given the current resistance issue, are needed to maintain effective thrips management.

Primer registro, distribución y ecología de Diplophos proximus (Gonostomatidae, Teleostei) en el Pacífico colombiano

The first findings and distribution of larvae of the species Diplophos proximus, family Gonostomatidae, in the Pacific of Colombia are presented. The analyzes show larvae between Bahía Málaga and Tumaco (limits with Ecuador), with low abundances during the seasons of September 2003 and 2005, July and December 2010, December 2013, February-March 2014, June 2016 and June and September 2017, always collected at stations located more than 113 km away from the coast and around Malpelo island. The larvae are elongated and have noticeable changes during development, initially oval eyes, poorly pigmented body without photophores and finallyrounded eyes, dorsal pigments and photophores during transformation. The present work contributes with information about distribution and ecology of larvae of D. proximus becoming the first records of catches for the Colombian Pacific, including the description of the larval stages found.

Distributions of settlers suggest greater dispersal and mixing of Ostrea chilensis larvae in Foveaux Strait, New Zealand

ABSTRACTThe Foveaux Strait oyster (Ostrea chilensis) fishery in southern New Zealand comprises many localised populations (oyster beds) that have survived disease mortality and 150 years of fishing. The reproductive biology of O. chilensis underlies the assumption that these populations are self-recruiting. A three-year study using passive, artificial collectors deployed in a gradient design around an isolated natal population investigated the hypothesis of self-recruitment. Spat settlement patterns measured the distributions of competent larvae as indicators of dispersal. This research also investigated the relationship between settler and brooder densities. Settler densities were not predicted by direction along or across the current, distance from the focal population, or by brooder densities. Settlement was widespread, and settlement patterns imply greater dispersal and larval mixing than previously reported. The swift currents and variable pelagic larval duration may enhance mixing and connectivity between populations. Demographically open recruitment should provide some resilience to disease mortality and fishing.

Spatiotemporal distribution of fish eggs and larvae in the Huanghe (Yellow) River estuary, China in 2005–2016

Decreasing fish resources in estuaries is a subject of anthropogenic activities. Studies of the spatiotemporal distribution of fish eggs and larvae can help identify the status and processes underlying recruitment in a fishery. As the fifth largest river estuary in the world, the Huanghe (Yellow) River estuary (HRE) is a typical estuary that has been seriously affected by human activities. Annual surveys on ichthyoplankton and environmental factors were conducted in the months of May of 2005 and 2009–2016 in the HRE to investigate the spatiotemporal distribution of fish eggs and larvae and the associated influencing factors. A total of 23 and 20 species of eggs and larvae, respectively, were collected. The dominant orders were Perciformes (51.2%) and Clupeiformes (25.6%). The average number of fish species eggs and larvae were 6.0 and 4.1 in average abundance of 0.91 and 0.13 ind./m3, respectively. The dominant species were mainly low-commercial-value small-sized fishes, such as Clupanodon punctatus, Harengula zunasi, and Acanthogobius, whereas certain traditional commercial fishes, such as Trichiurus lepturus, and Clupea pallasii, were not seen. Analysis of the fish egg and larval community revealed four temporal assemblages and two spatial assemblages. Salinity was the main factor on the spatial distribution of ichthyoplankton communities, the species number and Shannon-Weiner diversity index (H′) of the fish egg and larval community near the river mouth with lower salinity were significantly lower than the community far away from the river mouth with higher salinity. In addition, increases of water temperature promoted the number and abundance of fish species eggs, and the areas of abundant prey tended to have a more diversified and abundant of ichthyoplankton species. In overall, overfishing, dam construction, and other human activities were the main drivers that led to the substantial decline in fishery resources in the HRE.

Abundance and distribution of Sardinella tawilis (Herre, 1927) larvae in Lake Taal, Philippines

As part of the conservation efforts to address the declining population of the only freshwater Sardinella (Family Clupeidae) endemic to Lake Taal, a two-year study was conducted to determine the possible spawning grounds of Sardinella tawilis (Herre, 1927) by identifying the spatial and temporal distribution of its larvae. Fish larval samples were sorted from ichthyoplankton samples collected monthly in selected sampling stations in the lake. The morphologically identified Clupeidae larvae were determined to be S. tawilis genetically. They appeared only during March to May, with maximum abundance reaching from 700 to 1,700 ind 100m-3 during April 2015. Among the 10 water, 5 weather, and 11 biological parameters analyzed using Redundancy Analysis (RDA), temperature and other weather parameters largely influenced the temporal distribution of tawilis larvae. In terms of spatial distribution, the stations on the eastern bay of the lake showed an abundant and consistent presence of tawilis larvae for two years. Other stations which showed the presence of tawilis larvae include the southern portion of the lake, as well as in stations south to southwest area of Volcano Island. The seasonal and site-specific occurrence of tawilis larvae confirmed its spawning season and potential spawning grounds, which can serve as a scientific basis in the establishment of a Tawilis Reserve Area, as stipulated in the Unified Rules and Regulations for Fisheries in the Taal Volcano Protected Landscape Management Plan (TVPL-MP 2011).

川口水域におけるアユ仔稚魚の分布・回遊・成長

川口水域におけるアユ仔稚魚の分布・回遊・成長

Fine scale depth regulation of invertebrate larvae around coastal fronts

AbstractVertical migrations of zooplankters have been widely described, but their active movements through shallow, highly dynamic water columns within the inner shelf may be more complex and difficult to characterize. In this study, invertebrate larvae, currents, and hydrographic variables were sampled at different depths during and after the presence of fronts on three different cruises off the southern coast of South Africa. Internal wave dynamics were observed in the hydrographic data set but also through satellite imagery, although strong surface convergent currents were absent and thermal stratification was weak. During the first two cruises, fronts were more conspicuous and they preceded strong onshore currents at depth which developed with the rising tide. Vertical distributions of larvae changed accordingly, with higher abundances at these deep layers once the front disappeared. The third cruise was carried out during slack tides, the front was not conspicuous, deep strong onshore currents did not occur afterward and larval distributions did not change consistently through time. Overall, the vertical distributions of many larval taxa matched the vertical profiles of shoreward currents and multivariate analyses revealed that these flows structured the larval community, which was neither influenced by temperature nor chlorophyll. Thus, the ability to regulate active vertical positioning may enhance shoreward advection and determine nearshore larval distributions.

Effect of carcass model on maggot distribution and thermal generation of two forensically important blowfly species, Chrysomya megacephala (Fabricius) and Chrysomya rufifacies (Macquart)

BackgroundAt feeding stage, blowfly larvae (Diptera: Calliphoridae) form aggregation to facilitate the breakdown of a human body after death. The aggregation structure of blowfly larvae could probably be different depending on fly species and food size. In forensic investigations, corpse size does not only affect the internal temperature after death, but it could also potentially influence the distribution, aggregation temperature, and species of flies that inhabit a corpse. However, there is no reference available to explain how these factors could affect maggot distribution pattern and thermal generation. The best way to answer this is by accessing blowfly aggregation on multiple forensic entomology animal models of different sizes. Thus, this research is a preliminary assessment to determine maggot aggregation structure and its thermal generation in three carcass species which are commonly used as a surrogate for human corpses in Malaysia.MethodologyFrequency of Chrysomya megacephala (Fabricius) and Chrysomya rufifacies (Macquart) aggregations at a different location in carcass was determined. Aggregation temperature, depth, perimeter, area, and volume of tightly packed aggregations were measured. These variables were compared to ambient temperature and relative humidity. Correlation analysis was performed to access any relationship between each variable.ResultsAggregation temperature was found strongly correlated to carcass temperature (r = 0.65, p < 0.05), moderately correlated to carcass ground temperature (r = 0.57, p < 0.05), and weakly correlated to aggregation depth (r = 0.21, p < 0.05), relative humidity (r = 0.06, p = 0.35), and ambient temperature (r = 0.01, p = 0.89). The rate of carcass loss was significantly influenced by carcass model (p < 0.05). The frequency of Chrysomya megacephala (Fabricius) (Diptera: Calliphoridae) aggregation was more in rat carcasses, while for rabbits and macaques, Chrysomya rufifacies (Macquart) (Diptera: Calliphoridae) was more frequent. Aggregations of Chrysomya rufifacies were frequently observed located below carcasses while Chrysomya megacephala were observed mostly in the mouth and genitalia. Chrysomya rufifacies aggregations have produced higher temperature compared to Chrysomya megacephala.ConclusionCarcass model was proven to be a critical factor in larval aggregation distribution and temperature. Therefore, this preliminary study has pointed out the necessity of proper selection of animal model for forensic entomology study. Food source characteristics, particularly body size, could play a significant factor in larval aggregation distribution and thermal generation, therefore making this factor important when making postmortem interval (PMI) estimation based on larval growth.

Variability of euphausiid larvae densities during the 2011, 2012, and 2014 summer seasons in the Atlantic sector of the Antarctic

Euphausiid larvae were collected in the Weddell Scotia Confluence region in summer 2011, in the West Antarctic Peninsula and Scotia Sea in 2012, and in the South Orkneys Shelf in 2014. From 2011 to 2014 the larval stages geographic distribution and the distribution of water masses were consistent with published information. The densities observed were compared between the cruises and with the 1981 and 1995 values by means of a kernel estimate of absolute and relative densities at a fixed grid of points. The values of Thysanoessa macrura were higher in 2011 and 2012 and those of Euphausia superba were lower than those observed in 1981 and 1995. Euphausia frigida did not show significant variations in absolute density but their relative values were higher than those of E. superba. No significant variations were observed in absolute values between 1981 and 1995. The opposite pattern was found in 2014, with significantly higher densities of E. superba than those of T. macrura. No single factor could be identified to explain these variations in density, suggesting the existence of complex mechanisms coupling the reproductive biology with oceanographic phenomena. Their description will require ample spatial and temporal monitoring rather than locally detailed observations.

Characterizing spatial structures of larval fish assemblages at multiple scales in relation to environmental heterogeneity in the Strait of Georgia (British Columbia, Canada)

Spatial structures of larval fish in the Strait of Georgia (British Columbia, Canada) were quantified in the springs of 2009 and 2010 to investigate linkages to environmental heterogeneity at multiple scales. By applying a multiscale approach, principal coordinate neighborhood matrices, spatial variability was decomposed into three predefined scale categories: broad scale (&gt;40 km), medium scale (20∼40 km), and fine scale (&lt;20 km). Spatial variations in larval density of the three dominant fish taxa with different early life histories (Pacific herring (Clupea pallasii), Pacific hake (Merluccius productus), and northern smoothtongue (Leuroglossus schmidti)) were mainly structured at broad and medium scales, with scale-dependent associations with environmental descriptors varying interannually and among species. Larval distributions in the central-southern Strait were mainly associated with salinity, temperature, and vertical stability of the top 50 m of the water column on the medium scale. Our results emphasize the critical role of local estuarine circulation, especially at medium spatial scale, in structuring hierarchical spatial distributions of fish larvae in the Strait of Georgia and suggest the role of fundamental differences in life-history traits in influencing the formation and maintenance of larval spatial structures.

Ecological state of Severnaya Bight (Slavianka Bay, Peter the Great Bay, Japan Sea)

Oceanographic and chemical properties, sea currents, bottom topography and sediments in the Severnaya Bight (Slavianka Bay of Peter the Great Bay, Japan Sea) are considered on the base of all available data collected from 1965 to 2018. Mean and extreme values of the water parameters in the bight are determined for the first time. Seasonal and short-term tide-induced variations of the water temperature and salinity at certain depths are described. The environments influence on aquaculture is estimated. The hanging culture equipment can be mounted in the bight at the depth of no less than 10–12 m, whereas the bottom culture is possible in local areas with the depth of 6–10 m located in its northern and northwestern parts and southwestward from the Mininosok Inlet. In the north of the bight, the cultivated scallop is subjected to unfavorable influence of high water temperature and low salinity, but the water regime at the depth of 6–8 m, where the collectors and hatcheries are usually mounted, is relatively stable and favorable for the scallop cultivation, with rather rare and short-term rises of temperature (up to 25 °С), declines of salinity (to 24 ‰), and dissolved oxygen depletion (to 3.17 mL/L, or 58 %). Currents in the Severnaya Bight are strong enough for its waters renewal: 25–30 cm/s. The currents are almost reverse in the top of the bight; the semi-permanent cyclonic circulation develops in its main part that provides the water exchange with the open part of Peter the Great Bay and distribution of suspended solids, contaminants, bacteria, or larvae from marine farms or other sources over the bight. The non-tidal currents are almost twice stronger in winter than in summer.

A three year study of the phenology of insect larvae (Coleoptera, Diptera) in water-filled tree holes in the canopy of a beech tree

Water-filled tree holes are abundant microhabitats in forests worldwide and are inhabited by specialized communities of invertebrates. Despite their importance, the temporal dynamics of communities within and between years are largely unknown. Here, I present a case study on the phenology of insect larvae in two holes in a beech tree (lower and upper canopy) located in southern Germany over a period of three years. I asked whether water temperature and the characteristics of insect larvae at the community and population levels are similar in periodicity every year and whether they differ in the lower and upper canopy. The water temperature in tree holes differed greatly from air temperature, and this effect was more pronounced in the lower than in the upper canopy, which resulted in a lower probability of drying out occurring in the lower canopy. This was associated with a higher species richness in the lower canopy and greater abundance of drought tolerant species in the upper canopy. There was a significant periodicity in larval abundance, biomass, species richness and body size distribution of abundant species in both tree holes, but it was not seasonal. This result indicates that unpredictable drying out of tree holes are more important drivers of tree hole community dynamics than changes in water temperature. The community of larvae in the tree hole in the upper canopy lagged behind that in the lower canopy, which indicates that most species mainly colonize the more stable microhabitats in the lower canopy. Hopefully this case study will encourage future larger-scale phenological studies to test (1) whether the patterns observed in this study can be generalized over larger spatial scales and (2) the relative importance of abiotic and biotic drivers of the dynamics of communities in tree holes.

Distribution and abundance of mosquito larvae in Ohafia, Abia State, Nigeria

Quite a number of diseases are transmitted by mosquitoes. The abundance and distribution of mosquito vectors are related to the characteristics of larval habitats. A survey of the distribution and abundance of mosquito larvae was carried out at Nkporo and Abiriba Communities of Ohafia, Abia State, Nigeria. It was carried out during the dry and wet seasons from November 2014 to June 2015. The mosquito larvae were collected using dipper and pipette method from five mosquito habitats namely ground pools (58), household containers (213), domestic run-offs (49), gutters (55) and tree holes/leaf axils (43). A total of 2 641 mosquito larvae belonging to three genera and five species were collected. These were; Culex quinquesfaciatus (40%),Aedes aegypti (22%), Aedes albopictus (17%), Anopheles gambiae (14%), and Anopheles funestus (2%), Household containers had the highest number of larvae (60 %), while tree holes/leaf axils had the least (6%). From Nkporo, 53% of the larvae were collected while 47% was from Abiriba community. Anopheles funestus was recorded only in Nkporo community. However, the abundance of mosquito larvae sampled from the different habitats in the two communities were significantly different (X2 = 166,692, df = 16, P&lt;0,05) from each other. There were also significant differences in the seasonal distribution of mosquito larvae in both dry (X2 = 56,865, df = 12, P&lt;0,05) and wet (X2 = 22,241, df = 12, P&lt;0,05) seasons in Nkporo community and dry (X2=31,776, df = 12, P&lt;0,05) season in Abiriba community. These findings are useful in knowledge expansion on the vector ecology with particular interest on the type of habitat preference, this will be helpful in larval control programs.

Size-selective mortality of laboratory-reared Atlantic bluefin tuna larvae: evidence from microstructure analysis of otoliths during the piscivorous phase

Atlantic bluefin tuna (Thunnus thynnus) larvae show strong piscivorous feeding behavior at the very early larval stage and this enables them to grow at high rates. We conducted a laboratory experiment in which Atlantic bluefin tuna larvae were offered larval prey for the first time at different ages to simulate the early onset of piscivory at three treatments: yolk-sac larvae (YSL), delayed onset of piscivory (DYSL) and a solely planktivorous diet (Rotifers). The otolith microstructure was then used to compare the larval size distribution at the onset of the experiment with the estimated previous size-at-age of the survivors at the end of the experiment by back-calculation. Within a cohort, our results show size-selective mortality of the largest larvae independent of the differences in the timing of onset of piscivory and differences in growth patterns. The results also corroborate the rapid response of Atlantic bluefin tuna to piscivory in terms of growth reflected in the otolith increment widths. Being bigger did not infer a survival advantage and mortality rates did not decline with increasing larval size. Smaller size at a given age could under certain conditions and stages of development confer a survival advantage of individual members of a larval cohort when suitable small-sized prey is available.

Characteristics of egg and larval distributions and catch changes of anchovy in relation to abnormally high sea temperature in the South Sea of Korea

Characteristics of egg and larval distributions and catch changes of anchovy in relation to abnormally high sea temperature in the South Sea of Korea