Egg Abundance Research Articles

Distributions and seasonal abundances of krill eggs and larvae in the sub-Arctic Godthåbsfjord, SW Greenland

Distributions and seasonal abundances of krill eggs and larvae in the sub-Arctic Godthåbsfjord, SW Greenland

Spatial and seasonal patterns of ichthyoplankton assemblages in the Haizhou Bay and its adjacent waters of China

Surveys were conducted in five voyages in Haizhou Bay and its adjacent coastal area from March to December 2011 during full moon spring tides. The ichthyoplankton assemblages and the environmental factors that affect their spatial and seasonal patterns were determined. Totally 35 and 12 fish egg and larvae taxa were identified, respectively. Over the past several decades, the egg and larval species composition has significantly changed in Haizhou Bay and its adjacent waters, most likely corresponding with the alteration of fishery resources, which are strongly affected by anthropogenic activities and climate change. The Bray-Curtis dissimilarity index identified four assemblages: near-shore bay assemblage, middle bay assemblage and two closely related assemblages (near-shore/middle bay assemblage and middle/edge of bay assemblage). The primary species of each assemblage principally reflected the spawning strategies of adult fish. The near-shore bay assemblage generally occurred in near-shore bay, with depths measuring <20 m, and the middle bay assemblage generally occurred in the middle of bay, with depths measuring 20 to 40 m. Spatial and seasonal variations in ichthyoplankton in each assemblage were determined by interactions between biological behavioral traits and oceanographic features, particularly the variation of local conditions within the constraint of a general reproductive strategy. The results of Spearman’s rank correlation analysis indicated that both fish egg and larval abundance were positively correlated with depth, which is critical to the oceanographic features in Haizhou Bay.

Spatial distribution of infectious stages of the nematode Syngamus trachea within pheasant (Phasianus colchicus) release pens on estates in the South West of England: Potential density dependence?

The spatial distribution of the infectious stages of parasites with a direct life cycle is one of the most important factors influencing infectious disease dynamics, and acquisition rates will generally increase as the contact time between parasite and host increases. For animal species that are constrained by feeding opportunities, one might expect disease patterns to be highly skewed within confined systems. The aim of the present study was to identify to what extent, if any, eggs of avian parasites are aggregated within the release pen, and to evaluate what effect, if any, this aggregation had on the distribution of the adult stages within the host species. The abundance of Syngamus trachea eggs were highly aggregated within pens, with high levels of contamination driven by a combination of feeder placement, soil moisture and host-mediated heterogeneities in immuno-competence. The log mean and log variance of egg abundance was highly linear (R2=0.97–0.99), with an estimated slope (b) of between 1.79 and 1.97 for individual sites, and 2.11 when sites were combined, which indicated aggregation relative to an estimated Poisson slope of unity. Although the placement of feeders and environmental moisture could be contributing to parasite aggregation, density-dependent processes appear to be ensuring the population does not become too over or under-dispersed, in order to maintain the transmission-virulence equilibrium. To the best of our knowledge, this is the first paper to explicitly demonstrate the high spatial aggregation of eggs around feeding sites and the first to suggest possible density-dependent regulatory mechanisms stabilising disease dynamics between S. trachea and ring necked Pheasants (Phasianus colchicus).

Spawning activity of the four major Chinese carps in the middle mainstream of the Yangtze River, during the Three Gorges Reservoir operation period, China

Summary River flow alterations caused by dams have introduced many ecological problems, in particular a decline in aquatic species such as fishes. One compensatory measure is to create a hydrological process similar to the natural state with regard to the survival requirements of the fish. In recent years, the Three Gorges Reservoir (TGR) has introduced man-made flood by ecological operation experiments to facilitate spawning of the four major Chinese carps in the Yangtze River, China. To investigate the fish spawning activities and their responses to the TGR operation, eggs from the four major Chinese carps were sampled using conical drift nets in the middle mainstream of the Yangtze River, May to July in 2012 and 2013. Spawning timing, location, and scale of the four carps were studied and compared between the 2 years; key hydrological and environmental factors associated with spawning were determined by principal component analysis and stepwise regression analysis. Two factors were significantly positive when correlated with egg abundance: one was increasing rate of the river flow (flood amplitude), and the other was river transparency; only one factor, starting of the river flow (flooding occasions), was significantly and negatively correlated with the time of spawning. Comparison of egg abundance in one flood pulse response to different operation rules showed that flooding made by an ecological operation induced a larger scale of spawning than a conventional operation. The study implied that suitable flood conditions could produce a successful spawning event, and that the occasion and pattern of the flood process might result in different responses in fish spawning. Further research is required to develop more scientific monitoring designs in order to obtain accurate field data for both biotic and abiotic factors, and explore new research methods for egg abundance estimations combined with particle experiment and hydrodynamic modeling. This work is fundamental to improve the strategic decisions on reservoir operation and river management.

The beneficial root endophyte Piriformospora indica reduces egg density of the soybean cyst nematode

The soybean cyst nematode (Heterodera glycines) is a plant parasitic nematode that is a major plant pest worldwide and causes severe economic and yield losses. Piriformospora indica, a plant growth promoting fungus isolated from the Thar Deserts of western India, has been shown to protect a wide range of plants from various biotic and abiotic stresses. To evaluate the potential of P. indica to protect soybean (Glycine max) seedlings from damage by the soybean cyst nematode (SCN), we amended soil with two different concentrations of P. indica (2.5% and 5% w/w) and inoculated with second-stage juveniles (J2s) of SCN in each treatment. After 60days, abundance of nematode eggs was measured by calculating SCN egg population densities. We found that egg density/100cc soil was significantly decreased by 29.7% and 36.7% respectively in the soil amended with 2.5% and 5% P. indica compared to a control. Amendment with P. indica also had a strong growth and yield promoting effect in Soybean. Although root biomass was significantly decreased by 27.9% and 33.5% in the two treatments compared to the control, shoot biomass (dry weight) increased by 30.8% and 8.2% in the 2.5% and 5% P. indica treatments compared to the control. Additionally, plant development was accelerated and a 75% increase in flowering was observed between the 2.5% P. indica treatment and the control. We conclude that P. indica used as a soil amendment decreases abundance of the SCN in soil and has plant-growth promoting properties that may help offset yield losses due to plant parasitic nematodes.

Early life history pelagic exposure profiles of selected commercially important fish species in the Gulf of Alaska

A synthesis of nearly four decades of ichthyoplankton survey data from the Gulf of Alaska was undertaken to provide the most comprehensive information available on the early life history ecology of five focal species: Pacific Cod (Gadus macrocephalus), Walleye Pollock (Gadus chalcogrammus), Pacific Ocean Perch (Sebastes alutus), Sablefish (Anoplopoma fimbria), and Arrowtooth Flounder (Atheresthes stomias). This analysis of historical data, along with information from published studies, is presented here in the form of ecological reviews of the species during their planktonic phase. The reviews include descriptions of temporal and spatial patterns of exposure to the environment, and interpretation regarding associated sensitivities to environmental forcing. On a temporal scale, patterns in abundance of eggs and larvae are synthesized that characterize seasonal exposure to the pelagic environment, and interannual variation that is presumed to incorporate responses to long-term environmental forcing. Spatial patterns are synthesized to identify horizontal and vertical extent of egg and larval distributions, delineate areas of primary larval habitat, and illuminate egg and larval drift pathways. The observed patterns are discussed with respect to characterizing species early life history strategies, identifying long-term adaptations to the Gulf of Alaska environment, and associated resilience and vulnerability factors that may modulate early life responses to environmental forcing in this region. For each species, gaps in knowledge are identified and are concerned primarily with the period of transition between the larval and juvenile stage, and feeding habits and ecology across seasons, habitats and sub-intervals of early ontogeny. These early life history reviews advance our ecological understanding of the pelagic phase, and fine-tune our focus for the investigation of potential response mechanisms to environmental forcing at appropriate, species-specific temporal and spatial scales.

Comparison of the effects of two bongo net mesh sizes on the estimation of abundance and size of Engraulidae eggs

Abstract Studies of ichthyoplankton retention by nets of different mesh sizes are important because they help in choosing a sampler when planning collection and the establishment of correction factors. These factors make it possible to compare studies performed with nets of different mesh sizes. In most studies of mesh retention of fish eggs, the taxonomic identification is done at the family level, resulting in the loss of detailed information. We separated Engraulidae eggs, obtained with 0.333 mm and 0.505 mm mesh bongo nets at 172 oceanographic stations in the southeastern Brazilian Bight, into four groups based on their morphometric characteristics. The difference in the abundance of eggs caught by the two nets was not significant for those groups with highest volume, types A and B, but in type C (Engraulis anchoita), the most eccentric, and in type D, of the smallest volume, the difference was significant. However, no significant difference was observed in the egg size sampled with each net for E. anchoita and type D, which exhibited higher abundance in the 0.333 mm mesh net and minor axis varying from 0.45-0.71 mm, smaller than the 0.505 mm mesh aperture and the mesh diagonal.

Evidence forAedes aegypti(Diptera: Culicidae) Oviposition on Boats in the Peruvian Amazon

Dengue vector Aedes aegypti L. is invading peri-urban and rural areas throughout Latin America. Our previous research in the Peruvian Amazon has shown that river boats are heavily infested with immature and adult Ae. aegypti mosquitoes, likely playing a major role in their long-distance dispersal and successful invasion. However, the presence of immature mosquitoes provides no information about the timing of oviposition, and whether it took place in the boats. Here, we used baited ovitraps deployed on river boats to test the hypothesis that Ae. aegypti oviposition occurs during boat travel. We deployed 360 ovitraps on 60 different barges during August and October of 2013, and February 2014 (with 20 barges sampled during each month). We found that Ae. aegypti mosquitoes in 22 individual ovitraps from 15 of the 60 barges (premise index 25%) across all sampling dates. Further, the distribution of Ae. aegypti egg abundance was highly aggregated: 2.6% of traps (N=7) were responsible for 71.8% of eggs found, and 1.5% of traps (N=4) were responsible for all (100%) of the larvae found. Similarly, 5% of boats were responsible for the 71.47% of eggs. Our results provide strong evidence that Ae. aegypti oviposition commonly occurs during boat travel. Baited ovitraps could represent a cost-effective means of monitoring and controlling mosquito populations on boats.

Revisiting Fisher: range size drives the correlation between variability and abundance of British bird eggs.

We evaluate the correlation between intraspecific variation in egg size and population size in breeding British birds. Using information on abundance, range occupancy, migration status and phylogenetic relationships among species, we show that a wider geographical distribution rather than larger population size per se best predicts egg size variability. A similar result applies to wing length variability. Results from a phylogenetic path analysis suggest that geographical variation is the most parsimonious causal explanation for high intraspecific variation in common species.

High Resolution Spatial Analysis of Habitat Preference of Aedes Albopictus (Diptera: Culicidae) in an Urban Environment.

Over the past decades, the Asian tiger mosquito (Aedes albopictus (Skuse, 1895)) has emerged in many countries, and it has colonized new environments, including urban areas. The species is a nuisance and a potential vector of several human pathogens, and a better understanding of the habitat preferences of the species is needed for help in successful prevention and control. So far, the habitat preference in urban environments has not been studied in Southern European cities. In this paper, spatial statistical models were used to evaluate the relationship between egg abundances and land cover types on the campus of Sapienza University in Rome, which is taken as an example of a European urban habitat. Predictor variables included land cover types, classified in detail on a high resolution image, as well as solar radiation and month of capture. The models account for repeated measures in the same trap and are adjusted for meteorological circumstances. Vegetation and solar radiation were found to be positively related to the number of eggs. More specifically, trees were positively related to the number of eggs and the relationship with grass was negative. These findings are consistent with the species' known preference for shaded areas. The unexpected positive relationship with solar radiation is amply discussed in the paper. This study represents a first step toward a better understanding of the spatial distribution of Ae. albopictus in urban environments.

Egg production and hatching success of Calanus chilensis and Acartia tonsa in the northern Chile upwelling zone (23°S), Humboldt Current System

Oxygen Minimum Zones (OMZ's) are expanding and intensifying as result of climate change, affecting Eastern Boundary Upwelling Systems. Local effects of vertical movements of OMZ's that result from changes in upwelling intensity could reduce or expand the oxygenated surface layer that most zooplanktonic species inhabit in coastal areas. Using the copepods Calanus chilensis and Acartia tonsa as model organisms, an experimental test of the impact of different dissolved oxygen (DO) concentrations (between 0.5 and 5mlL−1) on egg production and hatching success was carried out and compared with field estimations of egg production, female and egg abundance in Mejillones Bay (23°S). Abundance of C. chilensis was highly variability and no consistent pattern in egg production and hatching success was found across DO levels, whereas A. tonsa egg production had maximum values between 2.6 and 4.7ml O2 L−1 and hatching success was positively correlated with DO (r=0.75). In the field, temperature was the main factor controlling the dynamics of both species, while Chl-a and DO were also correlated with C. chilensis and A. tonsa, respectively. Principal Component Analysis showed that abundances of both copepods were controlled by temperature, stratification, OMZ depth, and Ekman transport, which together explained more than 70% of the total variance and were the main factors that modulated the populations of C. chilensis and A. tonsa in the upwelling zone of northern Chile (23°S). The differential responses of C. chilensis and A. tonsa to changes in DO concentrations associated with vertical movements of the OMZ suggest that C. chilensis may be better adapted to hypoxic conditions than A. tonsa, however both species are successful and persistent all year-round. We suggest that physiological responses of copepods could be used to evaluate population dynamics affected by the shoaling of OMZ's and the repercussions to trophic food webs of eastern boundary current systems.

Spatial and numerical relationships of arthropod communities associated with key pests of maize

AbstractPest management largely focuses on managing individual pest species with little concern for the diverse communities that co‐occur with key pests and potentially shape their population dynamics. During anthesis, we described the foliar arthropod communities on 53 maize farms throughout the region of eastern South Dakota. The resulting communities were examined for trends in local associations in the abundances of taxa with key pests in the system (rootworms [Diabrotica spp.], European corn borers [Ostrinia nubilalis], aphids and Western bean cutworm [Striacosta albicosta]) using regression analyses. Regional spatial clustering in the abundances of key pests with members of the community was explored using Moran's I test statistic. The distributions of rootworms and European corn borer were mapped. A total of 37 185 arthropods representing at least 91 taxa were collected in South Dakota maize; there was an average of 5.06 predators and 8.29 herbivores found per plant. Key pests were never found at economically threatening levels (with one exception for Diabrotica). Numerous species were consistently numerically associated with each of the key pests across the farms during anthesis. Occasionally, these pests shared species with which they were locally associated with; for example, coccinellid egg abundances were predictive of the abundances of all key pest species except rootworm adults. Spatial analysis across the region suggested that species co‐occurred with key pests based on local characteristics surrounding the fields, rather than as a result of regional characteristics. Exceptions were documented; namely aphids and Western bean cutworms that spatially clustered with a handful of other members of the community. The results of the study point out that the abundances of key pests of maize were interconnected through indirect associations in the abundances of other members of the community. These associations may be useful for manipulating maize agroecosystems to minimize the effects of maize pests.

Dynamics of abundance of eggs and larvae of common fish species in the central part of the Eastern Central Atlantic

Data on variation in the abundance of mass fish species at early stages of ontogenesis in different areas of the Eastern Central Atlantic in warm (June–November) and cold (December–May) seasons of 1994–2012 have been analyzed. The representatives of the mass species in the region are European pilchard Sardina pilchardus, common scad Trachurus trachurus, chub mackerel Scomber japonicus, round sardinella Sardinella aurita, Cunene horse mackerel T. trecae, and Atlantic bonito Sarda sarda. Within the economic zone of Morocco, variations in abundance of the representatives of the subtropical fauna (S. pilchardus, T. trachurus, and S. japonicus) at early stages of ontogenesis are similar over the entire area under study (32°–21°N). In the area of Mauritania (21°–16°N), variations in the abundance of the mass fish species of the tropical fauna (S. aurita, T. trecae, and S. sarda) at early stages of ontogenesis cannot be unambiguously compared with such variations in the area of Morocco because Senegal-Mauritanian populations of the species inhabit waters of different states and are not completely assessed by our surveys.

Fecundity of the pine processionary moth Thaumetopoea pityocampa (Lepidoptera: Notodontidae) at the southern edge of its distribution range

AbstractAnalysis of annual and plot variations of egg batches number of Thaumetopoea pityocampa at the southern limit of its distribution area and in Pinus halepensis afforestations situated in the Algerian sub-Saharan region showed that its fecundity depends on the density of its population, plots, years and interaction of plots-years. It appears that the high average abundance of egg batches/trees during the outbreak period of this pest insect exceeds 24. The real fecundity is the lowest in the Mediterranean Basin and suggests that local adaptation can occur. The low fecundity is not an obstacle to caterpillar survival under different selection pressures. It is compensated by merging of colonies during the larval cycle. Moreover, in this study we noted a significant correlation between the number of eggs and the size of egg batches deposited on needles or around small pine branches. Size of egg batches is also intimately linked to the length of adult female forewings, fresh weight of females and weight of their pupae. Females with a biennial cycle have a low potential fecundity compared to those with an annual one.

Environmental factors affecting larval fish community in the salt marsh area of Guadiana estuary (Algarve, Portugal)

Salt marsh areas in the Guadiana estuary are important nursery sites for many fish species of commercial and recreational value. More effective protection measures should be adopted as the area is highly affected by anthropogenic and natural threats. Studying larval fish communities in these impacted nursery areas will be relevant to the management of local ecosystems and to larval fish ecology in general. Spatial and seasonal distribution and the effect of environmental factors on the larval fish community of this ecosystem were studied for one year (April 2010 to March 2011). Larvae were sampled monthly in parallel with phytoplankton and zooplankton. Hydrological data and physical parameters were monitored. A decision tree model was used to assess the influence of environmental factors on the larval fish community. A total of 130 larvae and 1171 eggs were caught. Diplodus sargus, Sardina pilchardus, and Pomatoschistus microps were the most abundant larval fish species. The peaks of fish larvae abundance occurred in March and April. The output of the model demonstrates that the abundance of larval fish is determined by the abundance of eggs, zooplanktonic food, and water flood and flow. This study shows the importance of the Guadiana salt marsh as an area for fish nursery and highlights the need for conservation of this area.

Distribution and abundance of eggs and estimation of spawning stock biomass of anchovy,Engraulis encrasicolus(Linnaeus, 1758), in the south-eastern Adriatic Sea

Seasonal distribution and abundance of anchovy eggs were analysed during three scientific cruises carried out from summer 2006 to summer 2007 in the Boka Kotorska Bay, and one cruise in July 2008 in the open waters of the south-eastern Adriatic Sea. Daily egg production method (DEPM) was applied for the first time for estimation of the anchovy spawning stock biomass in the south-eastern Adriatic Sea. The daily egg production was 13–581 eggs day−1within the bay, and 42–110 eggs day−1in the open waters. Anchovy egg abundance was highest in spring inside the Bay of Kotor (one of the innermost and eutrophic sub-bays of the Boka Kotorska Bay), which indicates that the conditions for anchovy spawning are very favourable in this part of the Adriatic Sea, even when temperatures are below the optimum. This study has shown that the Boka Kotorska Bay is an area of very intensive spawning of anchovy, and that small-size anchovies live and spawn in the bay, and after spawning migrate towards open waters. The length at which 50% of anchovy were mature (L50) was calculated as 9.28 for females and 9.02 for males. Spawning stock biomass was at a stable level during the period of investigation.

Varying Effects of Common Reed Invasion on Early Life History of Northern Pike

AbstractThe invasion of North American wetlands by the Eurasian subspecies of common reed Phragmites australis australis is well documented, but very few studies have been conducted on its effects on freshwater fish communities. Northern Pike Esox lucius is one of several fish species using wetlands for reproduction and early development that could be affected by the spread of common reed. The effects of vegetation type (common reed stands, other reference plant assemblages) were evaluated on four aspects (egg deposition, abundance, growth, and feeding) of the early life history of Northern Pike in two St. Lawrence River wetlands in Quebec. During high water levels in 2009, the relative abundance of Northern Pike eggs was three times higher in the reference plant assemblages than in the common reed stands at the two study sites. In 2010, when water levels were extremely low and few other plant assemblages were accessible by fish, the relative abundance of eggs was two times higher in the common reed stands than in other plant assemblages within the only site available for sampling. In 2009, the relative abundance, length, and weight of age‐0 Northern Pike did not differ significantly between common reed stands and reference assemblages. Growth rate, condition, prey type, and relationship between digestive tract dry weight and total fish dry weight suggested slightly more favorable conditions in common reed stands in some cases or in reference assemblages in other cases (no consistent pattern between the vegetation types). Although common reed is still in the early invasion process in St. Lawrence River freshwater marshes, it does not seem to have any negative effects on Northern Pike early life history. However, little is known about the magnitude of common reed biomass accumulation, making it impossible to predict whether these stands, which are part of an ongoing invasion, will provide long‐term quality habitat.Received March 3, 2014; accepted October 10, 2014

Spatial distribution of sardine and anchovy early life stages along the eastern Adriatic Sea

Event Abstract Back to Event Spatial distribution of sardine and anchovy early life stages along the eastern Adriatic Sea Barbara Zorica1, Vanja Cikes Kec1*, Goran Brzulja1 and Viktor Kraljević1 1 Institute of Oceanography and Fisheries, Croatia Despite long-term investigations of the Adriatic Sea in general and extensive research on sardine and anchovy as ecologically and economically important fish species, knowledge concerning their spawning ecology, precisely their possible spawning grounds, is still incomplete. Therefore, two scientific surveys (January, July 2012) were performed, as target species spawn during different periods of the year (sardine - October to April (Sinovčić et al., 2007) and anchovy - April to September (Zorica et al., 2013)). Throughout these surveys, standard vertical plankton tows were made during the daylight at 72 stations in January and 60 stations in July using a WP2 sampler (mouth opening, 0.255 m2; mesh size, 0.200 mm). WP2 net was put vertically down during the calm sea to a depth of 100 m or to 5 m above the seabed in relatively shallow marine area (less than 100 m). Plankton samples were preserved in 4% buffered formalin and transported to the laboratory where they were analysed. Throughout ichtyoplankton analysis of samples collected during the winter survey a total of 506 sardine eggs and 348 larvae were sorted out. The mean sardine egg and larval abundance in the analysed period at positive stations was 57.8 +/- 77.4 eggs/m2 and 29 +/- 25.85 larvae/m2, with peaks of 396 eggs/m2 and 108 larvae/m2 at positive sampling stations. Concerning the summer survey and anchovy early life stages from obtained samples 1489 anchovy eggs and 1036 larvae were isolated. Average abundance of anchovy eggs and larvae was 145.26 +/- 201.27eggs/m2 and 115.11+/- 162.32 larvae/m2, respectively. The highest values of mentioned parameters at positive stations were 800 eggs/m2 and 952 larvae/m2. According to obtained results and their processing within Ocean Data View (odv.awi.de), revile that both species during 2012 spawn above the whole continental shelf and the areas of higher early life stages abundance overlap. Acknowledgements This study was supported by the Ministry of Agriculture of the Republic of Croatia, as a part of the research project “Defining the spatial and temporal periods of sardine and anchovy spawning in the Adriatic Sea". References Sinovčić, G., Zorica, B. and ČIKEŠ KEČ, V. (2007). Abundance and some biological characteristics of sardine, Sardina pilchardus (Walb.,1792), in the coastal and open sea waters of the Adriatic Sea (Croatia). In: I. Rožanić (Editor). Proceedings, Second Conference on Marine Technology, Rijeka, pp. 155-174. Zorica, B., Vilibić, I., Čikeš Keč, V. and Šepić, J. (2013). Environmental conditions conducive to anchovy spawning in the Adriatic Sea. Fish. Oceanogr. 22(1): 32-40. Keywords: Small pelagic, Eggs, Larvae, Adriatic sea, Mediterranean Conference: XV European Congress of Ichthyology, Porto, Portugal, 7 Sep - 11 Sep, 2015. Presentation Type: Poster Presentation Topic: Life Cycles, Migration and Connectivity Citation: Zorica B, Cikes Kec V, Brzulja G and Kraljević V (2015). Spatial distribution of sardine and anchovy early life stages along the eastern Adriatic Sea. Front. Mar. Sci. Conference Abstract: XV European Congress of Ichthyology. doi: 10.3389/conf.fmars.2015.03.00009 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 27 Oct 2015; Published Online: 04 Nov 2015. * Correspondence: PhD. Vanja Cikes Kec, Institute of Oceanography and Fisheries, Split, Croatia, cikes@izor.hr Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Barbara Zorica Vanja Cikes Kec Goran Brzulja Viktor Kraljević Google Barbara Zorica Vanja Cikes Kec Goran Brzulja Viktor Kraljević Google Scholar Barbara Zorica Vanja Cikes Kec Goran Brzulja Viktor Kraljević PubMed Barbara Zorica Vanja Cikes Kec Goran Brzulja Viktor Kraljević Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Estimating the Dependence of Spawning Frequency on Size and Age in Gulf of Mexico Red Snapper

AbstractIn 2011, a large multivessel survey was conducted to provide nearly synoptic sampling of Red Snapper Lutjanus campechanus throughout their reproductive season in the U.S. Gulf of Mexico. A total of 2,487 Red Snapper were caught with a female : male ratio that was approximately 1:1. The ovaries of 1,002 females were histologically examined. Females (n = 391) were found with spawning markers (postovulatory follicles and hydrated oocytes) throughout the study area, but primarily in outer shelf waters. Statistical models were developed to quantify and test the dependence of the proportion of females bearing spawning markers (spawning fraction) on female length and age, time of year, depth, gear type (vertical line or longline), or region (east or west of the Mississippi River). Most of the variance in spawning fraction was explained by the time of year; spawning fractions were generally low in spring, peaked in midsummer, and declined by fall. There was also strong statistical evidence of a positive relationship between spawning fraction and either age or length. The effects of region and gear type were not significant once time of year and size or age were accounted for. These results demonstrate the need to account for differences in the time of year and age structure of the population when the productivity of populations of Red Snapper are compared. For example, productivity has been hypothesized to be greater in the western Gulf than in the eastern Gulf, as evidenced by regional patterns of egg and larval abundance. Our results suggest that this regional difference is not due to any intrinsic difference in the biology of the fish, but simply a consequence of there being more large, old Red Snapper in the western Gulf. Recent stock assessments have indicated that Red Snapper are increasing in abundance and there is a need to continue monitoring to detect any possible compensation in reproduction.Received November 25, 2014; accepted April 2, 2015

Comparing models of Red Knot population dynamics

ABSTRACT Predictive population modeling contributes to our basic scientific understanding of population dynamics, but can also inform management decisions by evaluating alternative actions in virtual environments. Quantitative models mathematically reflect scientific hypotheses about how a system functions. In Delaware Bay, mid-Atlantic Coast, USA, to more effectively manage horseshoe crab (Limulus polyphemus) harvests and protect Red Knot (Calidris canutus rufa) populations, models are used to compare harvest actions and predict the impacts on crab and knot populations. Management has been chiefly driven by the core hypothesis that horseshoe crab egg abundance governs the survival and reproduction of migrating Red Knots that stopover in the Bay during spring migration. However, recently, hypotheses proposing that knot dynamics are governed by cyclical lemming dynamics garnered some support in data analyses. In this paper, I present alternative models of Red Knot population dynamics to reflect alternative...