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Horizontal Migration (horizontal + migration)
Selected AbstractsThe Influence of Invertebrate Predators on Daphnia Spatial Distribution and Survival in Laboratory Experiments: Support for Daphnia Horizontal Migration in Shallow LakesINTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 1 2007Adrianna Wojtal Abstract The behavioural response of Daphnia cucullata to the presence of the pelagic invertebrate predator Leptodora kindtii, and the predation rate of littoral dragonfly nymphs on this species were investigated under laboratory conditions. Results of this study revealed a strong hiding response of Daphnia cucullata in the presence of the predatory cladoceran, L. kindtii, which was similar to the response of Daphnia in the presence of juvenile perch. This suggests that pelagic invertebrate predators may cause Daphnia to hide in the littoral zone which could result in increased exposure to predation by littoral invertebrates. A strong influence of dragonfly nymphs on D. cucullata, both in the presence and absence of macrophytes, was found. The average predation rate of Odonata larvae was about 5 prey ind,1 h,1 and did not differ significantly between treatments. Quantification of dragonfly pressure on Daphnia populations will require cross-verification with field experiments since in the natural conditions Daphnia seeks a shelter in the vegetation stands against predation by Leptodora, despite the occurrence of odonates. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] A prime inference on genetic diversity (RAPDs) in the marine fish Atherinella brasiliensis (Teleostei, Atherinopsidae) from Southern BrazilACTA ZOOLOGICA, Issue 2 2010Maria Cristina Da Silva Cortinhas Abstract Da Silva Cortinhas, M. C., Glienke, C., Prioli, A. J., Noleto, R. B., Matoso, D. A. and Cestari, M. M. 2010. A prime inference on genetic diversity (RAPDs) in the marine fish Atherinella brasiliensis (Teleostei, Atherinopsidae) from Southern Brazil. ,Acta Zoologica (Stockholm) 91: 242,248 As a result of the importance of Atherinella brasiliensis in estuarine environments, random amplified polymorphic DNA (RAPD) markers were used to verify the genetic diversity in A. brasiliensis from two different places in Paranaguá Bay (Paraná State) and one from the Conceição Lagoon (Santa Catarina State). Cytogenetic data have shown a high karyotypic diversity in some populations, although in others this peculiarity demonstrates rearrangements such as heterochromatinization. In the present study, a low level of genetic structuring between the samples from Conceição Lagoon compared with the others was observed through principal coordinate analysis (PCO), analysis of molecular variance and Mantel test according to 79 RAPD markers. As this specie does not perform horizontal migration and the individuals of Conceição Lagoon are isolated, three hypotheses are proposed to explain the results: (i) similar environments may show homogeneous populations not depending on the geographical distance, (ii) because vicariant events that formed the bays occurred in a recent period, the fragmentation effects over the structuring of the genetic diversity may still be low and not totally detectable by the RAPD technique and (iii) the isolation time or the number of generations may not be enough to promote a possible differentiation and genetic structuring between the specimens of these three places. The specimens of these places present a low level of differentiation and genetic structuring so we can consider them as a unique homogeneous population. [source] The role of macroinvertebrates and fish in regulating the provision by macrophytes of refugia for zooplankton in a warm temperate shallow lakeFRESHWATER BIOLOGY, Issue 10 2010MARÍA de los ÁNGELES GONZÁLEZ SAGRARIO Summary 1.,The zooplankton often undergoes diel horizontal migration (DHM) from the open water to the littoral of shallow lakes, thus avoiding predators in the former. This behaviour has functional impacts within the lake, as it enhances zooplankton survival, increases their control of phytoplankton and tends to stabilise the clear water state. However, most of the evidence supporting this migration pattern comes from cold north temperate lakes, and more evidence from tropical and subtropical areas, as well as from southern temperate areas, is needed. 2.,We conducted a field study of the diel horizontal and vertical migration of zooplankton, and the horizontal distribution of potential predatory macroinvertebrates and fish, over two consecutive days in the summer in a temperate lake in the southern hemisphere. We took zooplankton samples at two depths, at three sampling stations (inside beds of aquatic macrophytes, at their edge and in open water) along three transects running from the centre of a bed of Ceratophyllum demersum to open water. At each sampling station, we also took samples of macroinvertebrates and fish and measured physical and chemical environmental variables. 3.,Zooplankton (pelagic cladocerans, calanoid copepods and rotifers) avoided the shore, probably because of the greater risk from predators there. Larger and more vulnerable cladocerans, such as Diaphanosoma brachyurum and Moina micrura, were two to four times more abundant in open water than at the edge of or inside beds of macrophytes, respectively, by both day and night. Less vulnerable zooplankton [i.e. of medium body size (Ceriodaphnia dubia) or with the ability to swim fast (calanoid copepods)] were distributed evenly between open water and the edge of the plant beds. Small zooplankton, Bosmina huaronensis and pelagic rotifers, showed an even distribution among the three sampling stations. Accordingly, no DHM of zooplankton occurred, although larger organisms migrated vertically inside C. demersum stands. 4.,Macrophytes contained high densities of predatory macroinvertebrates and fish. The predator assemblage, composed of large-bodied macroinvertebrates (including odonates and shrimps) and small littoral fish, was permanently associated with submerged macrophytes. None of these groups moved outside the plant beds or changed their population structure (fish) over the diel cycle. 5.,Submerged macrophyte beds do not represent a refuge for zooplankton in lakes where predators are numerous among the plants, implying a weaker top-down control of phytoplankton biomass by zooplankton and, consequently, a more turbid lake. The effectiveness of macrophytes as a refuge for zooplankton depends on the associated assemblage of predatory macroinvertebrates and fish among the plants. [source] Individual-based models of cod movement and population dynamicsJOURNAL OF FISH BIOLOGY, Issue 2003H. J. Edwards Many fish species undergo seasonal changes in distribution, as a result of horizontal migrations between feeding, nursery and spawning grounds. Exploring the processes involved in these movements may be the key to understanding interactions with other species, man and the environment, and is therefore crucial to effective fisheries management. Recent tagging experiments providing information on the distribution of migratory fish stocks have indicated pronounced regional and temporal differences in the migratory behaviour of cod, suggesting complex interactions between this commercially important fish species and the environment. This paper presents a model of the horizontal movements of demersal fish, principally cod, using an individual-based modelling approach to explore and predict the relationship between demersal fish movements and key environmental and ecological factors. The model simulates the basic biological processes of growth, movement and mortality, and is driven by the analysis of physical tagging data recorded by electronic data storage tags (DSTs). Results show that the incorporation of behavioural data from DSTs into spatially explicit individual-based models can provide realistic simulations of large-scale fish stocks, thus giving a better understanding of their basic ecology and allowing more effective management of commercially important fish species. Possibilities of future improvements and extensions to the model are discussed. [source] | ||||||||||