Live-bearing fish start hunting for mobile prey within hours after birth, an example of extreme precociality. Because prenatal, in utero, development of this behaviour is constrained by the lack of free-swimming sensory-motor interactions, immediate success after birth depends on innate, evolutionarily acquired patterns. Optimal performance however requires flexible adjustment to an unpredictable environment. To distinguish innate from postnatally developing patterns we analysed over 2000 prey capture events for 28 metallic livebearers (Girardinus metallicus; Poeciliidae), during their first 3 days after birth. We show that the use of synchronous pectoral fin beats for final acceleration and ingestion is fixed and presumably innate. It allows for direct, symmetrical control of swimming speed and direction, while avoiding head yaw. Eye movements and body curvatures, however, change considerably in the first few days, showing that eye-tail coordination requires postnatal development. The results show how successful prey captures for newborn, live-bearing fish are based on a combination of fixed motor programmes and rapid, postnatal development.

No abstract

The large‐scale degradation of riparian ecotones and of the connectivity between rivers and their floodplains has resulted in a drastic decline of rheophilic fish populations in European temperate lowland rivers. Recent river restoration projects have had variable success in effectively restoring these fish populations. Knowledge on nursery habitat requirements is considered essential for effective population restoration. However, a detailed understanding of the role of habitat heterogeneity in young‐of‐the‐year (YOY) fish population development is limited. Therefore, we carried out a synthesis of the available knowledge on nursery habitat requirements of rheophilic fish species found in European temperate lowland rivers (<200 m elevation). From a total of 603 papers, 77 studies with primary information were selected, containing 390 associations between habitat features and YOY fish. As expected, most studies focused on static components of physical riparian habitat. Generally, YOY fish require habitats of shallow depth (<0.5 m), with slow‐flowing water (<0.2 m/s), gentle bank slope (<20°), variety in substratum types (fine sand to gravel), relatively warm water and high food availability. Surprisingly, no clear ontogenetic habitat shifts between larvae and juveniles were found, which may be explained by the limited spatial–temporal resolution of most studies. Since 2011, studies on habitat heterogeneity have increased, but few have explicitly assessed its role in relation to movement patterns of YOY fish for nursery success. Therefore, we recommend that future research focuses on fish movement patterns between habitat patches in heterogeneous (river‐floodplain) environments, to increase the knowledge base for effective recovery of rheophilic fish populations.

No abstract

A global survey of coral reefs reveals that overfishing is driving resident shark species toward extinction, causing diversity deficits in reef elasmobranch (shark and ray) assemblages. Our species-level analysis revealed global declines of 60 to 73% for five common resident reef shark species and that individual shark species were not detected at 34 to 47% of surveyed reefs. As reefs become more shark-depleted, rays begin to dominate assemblages. Shark-dominated assemblages persist in wealthy nations with strong governance and in highly protected areas, whereas poverty, weak governance, and a lack of shark management are associated with depauperate assemblages mainly composed of rays. Without action to address these diversity deficits, loss of ecological function and ecosystem services will increasingly affect human communities.

Understanding how reef-associated sharks utilise coastal reef habitats throughout their ontogeny is essential for their effective management. In this study, we assessed the distribution of sharks in the northern Caribbean Netherlands (Saba, Saba Bank and St Eustatius) and ontogenetic shifts in habitat and depth use of the 2 most observed species: Caribbean reef shark Carcharhinus perezi and nurse shark Ginglymostoma cirratum. We used stereo baited remote underwater video (stereo-BRUV) surveys at 376 sites. A total of 126 shark sightings (6 species) were recorded, with C. perezi (n = 72) and G. cirratum (n = 42) most frequently observed. The probability of recording at least 1 shark per deployment ranged from 0.19 to 0.37 and is comparable with shark occurrences in the small number of other stereo-BRUV studies in the Wider Caribbean Region. Habitat type was the most important factor driving reef-associated shark occurrences, with the highest probability of observing C. perezi and G. cirratum in soft-coral habitat. Additionally, occurrences of C. perezi were significantly influenced by the management zone, with highest probabilities of occurrence in no-fishing zones. Almost all observed reef-associated sharks (95.6%) were juveniles, indicating that the study area may be a nursery area. Overall, both species were observed in deeper waters with increasing size, indicating ontogenetic shifts in depth use. Our findings imply that protected areas should not be limited to a single habitat or depth, but focus on protecting a large area with the range of habitats and depths necessary for reef-associated sharks to complete their life cycle.

Lowland river-floodplain systems, such as the Rhine, contain a complex gradient of aquatic and terrestrial habitats that contribute to a high level of biological and structural diversity, ranking them among the most diverse and productive freshwater ecosystems in the world (Welcomme 1979;Junk et al. 1989;Ward et al. 1999). The ecological importance of the Rhine was however hardly recognised until the 1970s. In the past, poor water quality as a result of water pollutants (Wolff 1978), regulated discharges (Cowx & Welcomme 1998), and extensive river modifications resulted in a major decline in floodplain habitat diversity, availability, and quality. This had a major impact on its ecological functioning (Van Urk & Smit 1989; Van den Brink et al. 1996;Middelkoop 1997). Numerous ecological groups, especially (migratory) riverine fishes, are sensitive to changes in water quality and habitat availability, and their populations have severely declined as a result (