Georgiadis, M., Mavraki, N., Koutsikopoulos, C., & Tzanatos, E. (2014). Spatio-temporal dynamics and management implications of the nightly appearance of Boops boops (Acanthopterygii, Perciformes) juvenile shoals in the anthropogenically modified Mediterranean littoral zone. Hydrobiologia, 734(1), 81–96.
Abstract: A remarkable phenomenon of dense Boops boops shoals appearing almost adjacent to the shoreline during nighttime is known to the locals of island communities of the Aegean Sea (eastern Mediterranean). In this work, we investigated this appearance testing the hypotheses that (a) it may occur only in anthropogenically modified locations (as suggested by previous observations), (b) the migration pattern to the littoral is not arbitrary but synchronized to the sunset/sunrise, (c) fish abundance is affected by location, season and/or natural (moon) light fluctuations. Quantitative sampling included visual observations from the coast at five stations in Syros (Cyclades, Greece) from July 2009 to September 2010. Both hypotheses concerning occurrence only in anthropogenically modified locations and timing with sunset/sunrise were confirmed. Fish abundance was modelled using generalized additive models, demonstrating a seasonal pattern and revealing significant differences among sampling stations, but no moon-phase effects. The phenomenon investigated here has implications for fisheries management, as the shoal proximity to the shore renders them prone to illegal harvesting (seasonally at high abundances), aggravating the problem of illegal, unreported and unregulated fishing. Further considerations on the integrated management of the coastal zone arise, especially concerning the effects of habitat structural modification and light pollution.
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Hou, Z. - S., Wen, H. - S., Li, J. - F., He, F., Li, Y., Qi, X., et al. (2019). Effects of photoperiod and light Spectrum on growth performance, digestive enzymes, hepatic biochemistry and peripheral hormones in spotted sea bass (Lateolabrax maculatus). Aquaculture, 507, 419–427.
Abstract: Growth performance, digestive and metabolic activities, and contents of peripheral hormones of spotted sea bass (Lateolabrax maculatus) juveniles were evaluated under natural light and three different light spectrums (white, blue and red) in combination with three photoperiods (light: dark cycle, 12: 12-h, 18: 6-h and 24: 0-h). Bass in 18-h blue light environment displayed the best growth performance and digestive enzyme activities, while red light environment significantly impeded growth and digestive enzyme activities. Altered contents of melatonin, cortisol, thyroid hormones (T3 and T4), and testosterone (T) were observed in bass reared in red light, suggesting that red light could disturb endocrine homeostasis associated with biological rhythm (melatonin), stress coping (melatonin and cortisol), growth and development (T3 and T4), and aggressive behavior or hyperactivity (T3, T4 and T). Impaired growth performance might be due to energy used to cope with stress. We concluded that the red spectrum environment was stressful to spotted bass and the selection of appropriate light conditions (such as 18-h blue light) might lead to a beneficial outcome for spotted sea bass culture.
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Imsland, A. K., Roth, B., Foss, A., Vikingstad, E., Stefansson, S. O., Pedersen, S., et al. (2009). Long-term effect of photoperiod manipulation on growth, maturation and flesh quality in Atlantic halibut. Aquaculture Research, 40(11), 1260–1269.
Abstract: The aim of this study was to investigate the effect of continuous light at different stages during the production cycle of Atlantic halibut Hippoglossus hippoglossus L. on growth, age at first maturity, endocrine parameters and flesh quality. A group of juvenile halibut [mean (SD), initial weight 191.3 g (44.7)] was reared in indoor tanks under ambient temperature conditions for 38 months until harvesting (mean final weight, 4.6 kg). The entire photoperiod experiment was divided into four phases, where the fish in each phase were exposed to either natural photoperiod (62°33′N) or continuous light (L). Thus, the following five photoperiod combinations were tested: (a) Control group (NNNN), (b) Group 2A (NLNN), (c) Group 2B (NNLN), (d) Group 2C (NNNL) and (e) Production group (LNNN). Exposure to continuous light stimulated growth, and the final mean weights of Groups 2A and 2B were 23% and 11% higher than those of the Control group (NNNN). The final plasma 11-ketotestosteron levels were lower in Groups 2A (2.94 ng mL−1) and 2B (2.46 ng mL−1) compared with the Control (5.29 ng mL−1), Group 2C (5.09 ng mL−1) and the Production group (4.78 ng mL−1) during spring 2007 (age 4 years), indicating higher age at first maturity in Groups 2A and 2B. Photoperiod regime had only a minor, and transient, effect on flesh-quality traits of the fish, whereas a significant seasonal effect was seen with a tendency towards increased gaping, lower pH, lower hardness and lower shear force in July compared with December and March.
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Kupprat, F., Holker, F., Knopf, K., Preuer, T., & Kloas, W. (2021). Innate immunity, oxidative stress, and body indices of Eurasian perch Perca fluviatilis after two weeks of exposure to artificial light at night. J Fish Biol, in press.
Abstract: Artificial light at night (ALAN) can disrupt biological rhythms of fish and other vertebrates by changing the light information of the nocturnal environment. Disrupted biorhythms can impair the immune system of vertebrates as it has been shown for conditions with continuous illumination or long-day photoperiod in many vertebrates, including fish. However, this has not been shown so far under typical ALAN scenarios with high light intensities during day and low light intensities at night. Therefore, we measured proxies for the innate immune system and oxidative stress as well as body indices of Eurasian perch Perca fluviatilis under a wide range of intensities of nocturnal illumination. We found no changes in parameters of the innate immune system and no significant changes in proxies for oxidative stress after two-week exposures to nocturnal illuminance ranging from 0.01 lx to 1 lx in one experiment or from 1 lx to 100 lx in a second experiment. A decrease in the hepatosomatic index at the highest tested light intensity of 100 lx compared to the dark control was the only significant difference in all parameters among treatments. After two weeks of exposure, ALAN does not seem to seriously challenge the innate immune system and seems to cause less oxidative stress than expected. Our results contradict findings from other studies applying continuous illumination or long-day photoperiod and highlight the importance of further research in this field. Since ALAN represents a sustained modulation of the environment that may have cumulative effects over time, long-term studies are required for a better understanding of how ALAN modulates the health of fish. This article is protected by copyright. All rights reserved.
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Kupprat, F., Kloas, W., Krüger, A., Schmalsch, C., Hölker, F., & Cooke, S. (2020). Misbalance of thyroid hormones after two weeks of exposure to artificial light at night in Eurasian perchPerca fluviatilis. Conservation Physiology, 9(1).
Abstract: Artificial light at night (ALAN) can affect the physiology and behavior of animals because it alters the natural rhythm of light and darkness. Thyroid hormones (TH) are partially regulated by the light information of photoperiod and are involved in metabolic adjustments to daily and seasonal changes in the environment, such as larval and juvenile development, somatic growth and reproduction. ALAN can change photoperiodic information and might thereby lead to changes in thyroid metabolism, but so far research on this topic is scarce. Therefore, we tested in two different experiments the effects of nocturnal illumination at a wide range of light intensities on TH in plasma of Eurasian perch (Perca fluviatilis). Total 3,3′,5-triiodo-L-thyronine (T3) was significantly affected by ALAN and reduced at the highest tested intensity of 100 lx after only two weeks of exposure. Although total L-thyroxine (T4) was not significantly affected, the ratio of T3 to T4 tended to slightly decrease at 100 lx. In a second low-light experiment ALAN did not have clear effects on T3, T4 or the ratio of T3 to T4 at intensities between 0.01 lx and 1 lx. The results show first signs of endocrine disruption in thyroid metabolism after a relatively short ALAN exposure of two weeks under high-intensity streetlight conditions. Misbalanced thyroidal status can have serious implications for metabolic rates as well as developmental and reproductive processes.
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