Patterns of movement and habitat use by tigerfish (Hydrocynus vittatus) in the Upper Zambezi River (Namibia)

Abstract

Patterns of movement and habitat use by tigerfish (Hydrocynus vittatus) in the Upper Zambezi River (Namibia) Un resumen en españ ol se incluye detrás del texto principal de este artículo.Abstract -During 6 November to 24 December 2000, 23 tigerfish [(Hydrocynus vittatus), 30-54 cm] were tagged with radio transmitters in the Zambezi River (Namibia) to record habitat utilisation during low, rising and high water levels. The fish were tracked, on average, every fourth day during 23 November to 18 May. Two movement patterns were detected. Approximately 50% of the fish moved <1000 m among tracking surveys, staying within 'defined' home ranges. The remaining fish showed consistent site fidelity for periods, with long distance movements (>1000 m) to new areas among residency periods. Overall, mean distance moved between tracking surveys was 1447 m. Home range size varied among individuals, with a 95% probability of localisation within an average area of 276,978 m 2 . The fish utilised a mean river stretch of 18,836 m (range ¼ 90-71,840). All the fish were recorded in the main stem, and on average, 95% of the fixes were in the main stem during low water. However, the fish used temporary flooded areas to an increasing extent during the rising and high water period, but did not undertake longdistance migrations into the floodplains. Fish were sometimes near vegetation, but were never recorded into or under vegetation.

Movement patterns and home range of wild and re-stockedArapaima gigas(Schinz, 1822) monitored by radio-telemetry in Lake Imiria, Peru

“…Possible explanations could be the suitability of these environments for resting, hiding from fishermen and also for foraging on their piscine prey, which abound in these vegetated shoreline ecotones (Frankiewicz et al., ; Petry et al., ). Such preferences were also observed in other large tropical predatory fishes in both rivers (Økland et al., ) and lakes (Nyboer and Chapman, ). The importance of floating vegetation for the distribution of A. gigas in Lake Imiria is particularly interesting because abundance has been found to be unrelated to macrophyte cover in the Mamirauá Reserve in Brazil (Arantes et al., ) despite the positive correlation observed between macrophyte cover and the abundance of other predatory fishes (Petry et al., ).…”

“…The choice of radio telemetry was driven by cost‐benefit considerations of the technique when compared to acoustic telemetry and by its relative ease of implementation in a remote area. In such studies the most commonly used parameter is the home range, which describes the amount of area occupied by an individual during a determined period of time (Dunn and Gipson, ; Crook, ; Økland et al., ; Koehn et al., ; Nyboer and Chapman, ). The home range calculations were made in earlier studies using the Minimum Convex Polygon (MCP) method, but have been replaced progressively by the Kernel Density Estimation (KDE) with the help of new computerized routines in combination with a Geographic information system (GIS) like HoRAE for Openjump, a free online package used in this study (Steiniger and Hunter, ).…”

Migration and movement profiles of a potadromous fish (Brachymystax lenok Pallas 1773) in a highly connected river system (Mongolia)

“…While B. lenok are morphologically adapted to feeding on the substrate with benthic macroinvertebrates as a major food source(Chanda et al, 2005;Olson, Jensen, & Hrabik, 2016), during the late afternoon in summer, B. lenok appeared to take advantage of the hatching aquatic invertebrates drifting on the river surface as is indicated by their mean surface depth during this period.Seasonal differences in the mean acceleration and depth of B. lenok at night are also attributed to fluctuating river discharge and water temperature. Although the exact spatial location of fish at night could not be explicitly determined within the acoustic receiver array, previous fisheries research in the river indicated that there is increased B. lenok capture when electrofishing on the Eroo River margins at night compared to electrofishing the same areas during the day (M. Schäffer, personal communication, 20 September 2012).…”

Blood lactate levels as a biomarker for angling-induced stress in tigerfishHydrocynus vittatusfrom the Okavango Delta, Botswana

“…The tigerfish Hydrocynus vittatus is not only the most sought-after freshwater angling fish in Africa, but is one of the most important predatory fishes in African waters (Winemiller and Kelso-Winemiller 1994, Skelton 2001, Økland et al 2005. Although abundant in certain areas throughout Africa, its numbers have declined in many rivers due to water extraction, pollution, obstructions such as dams and weirs, and fishing pressure (Steyn et al 1996, Skelton 2001).…”