Peak Abundance Of Larvae Research Articles

Patterns of parasitism by Amblyomma rotundatum (Ixodidae) on Rhinella schneideri (Bufonidae) in islands of São Francisco River, Minas Gerais, Brazil

Abstract: We sampled ticks from specimens of the rococo toad Rhinella schneideriby flannel dragging on two Islands located in the São Francisco River near the Três Marias hydroelectric dam, southeastern Brazil. A total of 120 toads was examined, of which 63 (52.5%) were parasitized only by Amblyomma rotundatumtotaling 96 larvae, 163 nymphs and 134 females. The burden of parasitism ranged from one to 43 ticks, with a mean intensity of infestation of 6.2±5.5 ticks per host. The tick A. rotundatumexhibited highly aggregated distribution. Peak abundance of larvae and nymphs occurred in the dry season (May to September), whereas peak abundance of females occurred in the wet season (October to April). We collected most ticks near the head and hind limbs of R. schneideri. The finding of two engorged A. rotundatumnymphs in the same resting places of two toads and the absence of this species in the dragged areas suggest a nidicolous behavior at the studied site.

Recruitment of striped bass in Chesapeake Bay: spatial and temporal environmental variability and availability of zooplankton prey

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 409:213-228 (2010) - DOI: https://doi.org/10.3354/meps08586 Recruitment of striped bass in Chesapeake Bay: spatial and temporal environmental variability and availability of zooplankton prey E. J. Martino1,2,*, E. D. Houde1 1University of Maryland Center for Environmental Science, Chesapeake Biological Laboratory, 1 Williams Street, Solomons, Maryland 20688, USA 2Present address: National Oceanic and Atmospheric Administration, Cooperative Oxford Laboratory, Oxford, Maryland 21654, USA *Email: ed.martino@noaa.gov ABSTRACT: Causes of recruitment variability in young-of-the-year (YOY) striped bass Morone saxatilis from Chesapeake Bay were investigated based on (1) surveys from 2001 to 2003 to document spatio-temporal variability in abundance of larval striped bass, zooplankton prey, and feeding success of larvae; (2) a synthetic analysis (1996, 1998, 1999, 2001 to 2003) to describe how environmental factors and prey affect recruitment success; and (3) a 10 yr analysis (1993 to 2002) of inter-annual differences in spatial and temporal patterns of copepods and cladocera eaten by striped bass larvae. Striped bass YOY recruitment levels varied >11-fold in the 6 years examined. In those years, mean daily freshwater flows from the Susquehanna River to the bay in March and April varied >2-fold and controlled distribution and apparent survival of striped bass larvae. Strong recruitments of YOY striped bass were associated with matches in space and time of larval striped bass and high concentrations of zooplankton prey, especially the copepod Eurytemora affinis and cladoceran Bosmina longirostris. The strongest year classes (1996, 2003) were produced in years of high freshwater flow, characterized by a high abundance of feeding-stage larvae and a spatio-temporal match between peak abundance of larvae and zooplankton prey. Enhanced feeding opportunities were most pronounced in high freshwater-flow years (1996, 1998, 2003), when larvae and zooplankton prey were strongly associated with, and apparently retained near, the estuarine turbidity maximum. First-feeding larvae fed more successfully in a high-flow year (2003; prey incidence 91%) than in a drier year (2001; prey incidence 35%). A regression model that may have forecasting potential was developed to describe recruitment of YOY striped bass for the years from 1985 to 2006. The model includes spring freshwater flow and air temperatures to predict age-0 striped bass recruitment strength (R2 = 0.65). Flow and temperature control environmental and hydrographic conditions that strongly influence spatio-temporal overlap of larval striped bass and zooplankton. The model provided accurate recruitment forecasts for 2007 and 2009, but was less successful in 2008, a year of exceptionally low recruitment. KEY WORDS: Chesapeake Bay · Striped bass · Recruitment variability · Larval fish · Zooplankton · Trophodynamics · Biophysical interactions Full text in pdf format PreviousNextCite this article as: Martino EJ, Houde ED (2010) Recruitment of striped bass in Chesapeake Bay: spatial and temporal environmental variability and availability of zooplankton prey. Mar Ecol Prog Ser 409:213-228. https://doi.org/10.3354/meps08586 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 409. Online publication date: June 23, 2010 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2010 Inter-Research.

Fish recruitment on floodplains: the roles of patterns of flooding and life history characteristics

Floodplain inundation in rivers is thought to enhance fish recruitment by providing a suitable spawning environment and abundant food and habitat for larvae. Although this model has not previously been tested in Australian rivers, it is often extrapolated to fishes of the Murray-Darling Basin. Fortnightly sampling of larvae and juveniles was conducted in the unregulated Ovens River floodplain during spring–summer of 1999 (non-flood year) and 2000 (flood year). The only species that increased in larval abundance during or shortly after flooding was an introduced species, common carp (Cyprinus carpio). Additionally, the peak abundance of larvae on the floodplain occurred during a rapidly declining hydrograph under low flow conditions in isolated billabongs and anabranches. The low use of the inundated floodplain for recruitment contradicts previous models. We propose a model of the optimum environmental conditions required for use of the inundated floodplain for fish recruitment. The model suggests that the notion of the flood pulse alone controlling fish recruitment is too simplistic to describe all strategies within a system. Rather, the life history adaptations in the fauna of the system and aspects of the hydrological regime such as duration and timing of inundation will control the response of a river's fish fauna to flooding.

Influence of Introduced Spawning Habitat on Yellow Perch Reproduction in Lake Madison, South Dakota

ABSTRACT Yellow perch (Perca flavescens Mitchill) populations often exhibit variable recruitment in eastern South Dakota. Lakes with erratic yellow perch recruitment are shallow and lack structure; consequently, habitat manipulation may be useful to enhance perch recruitment. The objective of this study was to determine the contribution of eggs deposited on a conifer tree reef toward overall larval yellow perch production in Lake Madison. The number of egg masses deposited on the reef and the mean number of eggs per mass were calculated and used to estimate the number of larvae produced on the reef. Peak abundance of larvae in the lake was estimated using a surface trawl. Results from two years indicated that the reef contributed 14 to 37% toward larval yellow perch production, although confidence intervals were large. Low numbers of egg masses observed per tree (0.13 to 0.44) relative to other studies lead us to conclude that several smaller reefs might have been a better design than a single, large reef.

Spawning season and migration of the myctophid fish Diaphus theta in the western North Pacific

The spawning season, spawning grounds, and migration of the myctophid fish Diaphus theta were studied in the western North Pacific, based on seasonal sampling and estimation of hatching dates. The peak abundance of larvae was observed in July in the transition waters between the Oyashio and Kuroshio fronts. The spawning season ranged from late March to early September, with a peak from May to July. Larvae and juveniles <40 mm in standard length were distributed in the transition waters, whereas larger individuals were collected in the Oyashio and the Western Subarctic waters. These results indicate that this species undergoes a horizontal spawning migration from the Oyashio and Western Subarctic waters into the transition waters crossing the Oyashio front.

Distribution and abundance of eggs, larvae and early juveniles of sauryScomberesox saurus scombroides(Richardson) off the south-western Cape, South Africa, 1977/78

The distribution patterns of saury eggs, larvae and early juveniles have been investigated over the continental shelf off the South-Western Cape from August 1977 to August 1978. Young saury tend to occupy water of 18°C or warmer in all seasons and are found offshore of the Benguela oceanic front when inshore upwelling is evident. Their distribution in the region appears to be linked to seasonal hydrography. Spawning in the study area occurs mainly between Cape Columbine and Cape Point, and to a lesser extent east of Cape Point. The ratio of large larvae and early juveniles to small larvae is greater off the West Coast than off the South Coast. Most spawning appears to take place in summer, with a peak abundance of larvae and early juveniles towards the end of this season. Instantaneous natural mortality was calculated: 5 – 30 mm, Z = 0,14·day−1; 30 – 100 mm, Z = 0,02·day−1. There is therefore a marked but unexplained decline in mortality shortly after the transition from the larval to the juvenile phase.

A Comparison of Dispersal Strategies in Two Genera of Brachyuran Crab in a Secondary Estuary

Seasonal occurrence and vertical distribution of larvae of two genera of brachyuran crab were studied in a secondary estuary flowing into Delaware Bay. Spawning in the xanthid crabRhithropanopeus harrisii occurred earlier with peak abundance of larvae in June and with a distinct decline in abundance in August. In contrast,Uca spp. larvae reached peak abundance in August. All zoeal stages ofR. harrisii were collected in the river suggesting that larvae of this species are retained in secondary estuaries near areas of prime adult habitat. Only zoea stage I larvae and megalopa ofUca spp. were collected in the river indicating that larvae of these speies may be flushed into the Delaware Bay and may not return to secondary estuaries near areas suitable for adult habitat until the megalopa stage is reached. It is not clear if this dispersal pattern is an active or passive process. *** DIRECT SUPPORT *** A01BY019 00004