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Bos, A. R., & Gumanao, G. S. (2012). The lunar cycle determines availability of coral-reef fishes at fish markets. J Fish Biol, 81(6), 2074–2079.
Abstract: During 139 visits between March 2009 and May 2011, it was found that the availability of reef fishes at a local fish market in the Philippines was highly affected by the lunar cycle. The number of vendors selling reef fishes was significantly lower (13.4%) during third lunar quarters (full moon periods) than during the first, second and fourth lunar quarters (40.2, 25.0 and 30.0%, respectively). It is recommended that the influence of the lunar cycle on fish availability is considered when designing sampling strategies for catch surveys.
Mehner, T. (2012). Diel vertical migration of freshwater fishes – proximate triggers, ultimate causes and research perspectives: Diel vertical migration in freshwater fishes. Freshwater Biology, 57(7), 1342–1359.
Abstract: 1. Diel vertical migrations (DVM) are typical for many cold-water fish species such as Pacific salmons (Oncorhynchus spp.) and coregonids (Coregonus spp.) inhabiting deep lakes. A comprehensive recent overview of DVM in freshwater fish has not been available, however.
2. The main proximate trigger of DVM in freshwater fish is the diel change in light intensity, with declining illumination at dusk triggering the ascent and the increase at dawn triggering the descent. Additional proximate cues are hydrostatic pressure and water temperature, which may guide fish into particular water layers at night.
3. Ultimate causes of DVM encompass bioenergetics efficiency, feeding opportunities and predator avoidance. None of these factors alone can explain the DVM in all cases. Multi-factorial hypotheses, such as the âantipredation windowâ combined with the thermal niche hypothesis, are more likely to explain DVM. It is suggested that planktivorous fish move within a layer sufficiently well illuminated to capture zooplankton, but too dark for predators to feed upon the migrating fish. In complete darkness, fish seek layers with a temperature that optimises bioenergetics efficiency. The strength of each factor may differ from lake to lake, and hence system-specific individual analyses are needed.
4. Mechanistic details that are still poorly explored are the costs of buoyancy regulation and migration, the critical light thresholds for feeding of planktivorous and piscivorous fish, and predator assessment by (and size-dependent predation risk of) the prey fish.
5. A comprehensive understanding of the adaptive value of DVM can be attained only if the behaviour of individual fish within migrating populations is explicitly taken into account. Size, condition and reproductive value differ between individuals, suggesting that migrating populations should split into migrants and non-migrants for whom the balance between mortality risk and growth rate can differ. There is increasing evidence for this type of partial DVM within populations.
6. Whereas patterns of DVM are well documented, the evolution of DVM is still only poorly understood. Because experimental approaches at realistic natural scales remain difficult, a combination of comprehensive data sets with modelling is likely to resolve the relative importance of different proximate and ultimate causes behind DVM in fish.
Perkin, E. K., Hölker, F., Tockner, K., & Richardson, J. S. (2014). Artificial light as a disturbance to light-naÃ¯ve streams. Freshw Biol, 59(11), 2235â€“2244.
Artificial light at night is prevalent in human-dominated landscapes, and streams in these landscapes can be expected to be affected by artificial lights. We hypothesised that artificial light at night would reduce the activity of aquatic insects, resulting in reduced drift rates, lower fish growth rates and lower leaf litter decomposition rates.
We tested these hypotheses by installing street lights to reaches in four forested, natural streams of coastal British Columbia each paired with a control reach. Cutthroat trout (Oncorhynchus clarkii) are the top predators in these streams and feed mostly on terrestrial and drifting aquatic invertebrates.
We found that the night-time drift of aquatic invertebrates in lit reaches was Ëœ50% of the drift in dark reaches. However, the density of emerging aquatic insects, the density of insects falling into reaches, leaf litter decomposition rate and the number and growth rate of trout caught were not significantly different between the dark and experimentally lit reaches.
We conclude that, while short-term exposure to artificial light during the summer changes invertebrate behaviour, it does not significantly alter other trophic levels in forested headwater streams. Our results suggest that low levels of artificial light do not strongly influence stream ecosystems, but future research should determine whether this is true for all seasons and longer-term exposure to light.