Change of foraging behavior of cormorants and the effect on river fish

Jepsen, Niels; Ravn, Henrik Dalby; Pedersen, Stig

doi:10.1007/s10750-018-3656-2

Cited by 28 publications

(19 citation statements)

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“…For recovery of PIT tags, Boel (2012) investigated the efficiency of ground scanning for PIT tags under the cormorant breeding colony in Lake Hald and evaluated this in combination with radiotelemetry. He found that 40% of the tags actually taken by cormorants were found in a colony by scanning (further described in Skov et al, 2013;Jepsen et al, 2018). Thus, this proportion takes into account the number of PIT tags regurgitated outside the colony as well as undetected tags in the colony (see also Frechette et al, 2012).…”

mentioning

confidence: 99%

“…Cormorants (Phalacrocorax spp.) are frequent predators of fish in European fresh waters (Čech, Čech, Kubečka, Prchalová & Draštík, 2008;Jepsen, Ravn & Pedersen, 2018;Keller, 1995;Klenke et al, 2012;Skov et al, 2013;Steffens, 2010), and may also impact fish populations in coastal areas (Hansson et al, 2017;Jepsen, Sonnesen, Klenke & Bregnballe, 2010). Some studies have found little effect of cormorant predation on wild fish populations in rivers or lakes (Boström, Lunneryd, Karlsson & Ragnarsson, 2009;Engström, 2001;Frechette et al, 2012;Kumadaa, Arimaa, Tsuboib, Ashizawab & Fujioka, 2013;Leopold, van Damme & van der Veer, 1998;Suter, 1995), whilst others have shown that cormorant predation influences fish populations (Jepsen et al, 2010;Klenke et al, 2012;Koed et al, 2006;Rudstam et al, 2004;Skov et al, 2013;Steinmetz, Kohler & Soluk, 2003).…”

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confidence: 99%

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The impact of Cormorant predation on Atlantic salmon and Sea trout smolt survival

Jepsen

Flávio

Koed

2018

Fisheries Management Eco

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confidence: 99%

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confidence: 99%

The impact of Cormorant predation on Atlantic salmon and Sea trout smolt survival

Jepsen

Flávio

Koed

2018

Fisheries Management Eco

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“…For example, predation by cormorants ( Phalacrocorax spp.) was estimated to have caused mortality of >70% of grayling tagged in Danish rivers across a 10‐year period (Jepsen et al., 2018), whilst Suter (1995) found no evidence to suggest a negative impact of cormorant predation on grayling population dynamics in a Swiss river.…”

Section: Discussionmentioning

confidence: 99%

Medium‐term environmental changes influence age‐specific survival estimates in a salmonid population

et al. 2021

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1. Human-induced environmental change is a major stressor on freshwater habitats that has resulted in the population declines of many freshwater species.Ontogenetic shifts in habitat use and associated (st)age-specific requirements mean that impacts of environmental stressors can influence (st)ages in a population differently, and yet relatively few studies of freshwater fish populations account for their detail.2. We aimed to identify environmental and biotic factors affecting survival estimated for six age-classes of a European grayling population in the River Wylye, UK over a 17-year period. We used a Bayesian age-structured state space model to estimate survival of grayling cohorts between subsequent life stages (eggs to age 5 adults) for 16 annual transitions (2003-2004 to 2018-2019), whilst accounting for imperfect sampling of the population. We quantified the effects of seasonal water flow and temperature, in-stream habitat and prey resource, and potential competitors and predators on survival between subsequent life stages. We used Bayesian variable selection to gauge their relative importance on survival.3. Grayling abundances declined during the study period (>75% in all age-classes), predominately driven by a loss of mature adults. Changes to seasonal flows negatively influenced their survival: increased days of summer low flow related to decreased survival of subadults and mature adults, and lower winter flows related to reduced recruitment of juveniles from eggs. Higher summer macrophyte cover negatively influenced juvenile and subadult survival and increasing days of high temperature in summer appeared detrimental to juvenile survival. Abundance of brown trout (a potential competitor and predator) did not negatively influence grayling survival. 4. Our results reveal the implications of environmental change on a salmonid population, where recent low summer flows and high temperatures, and below average winter flows, have negatively influenced grayling survival. These conditions appear to be becoming more frequent and persistent in our study river, which is towards the species' southern range limit, which could render the population vulnerable to climate change. Our study demonstrates how careful analysis of long-termThis is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

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“…Predation from cormorants in particular, has been documented to be an important factor for many populations of stationary and migrating river fish and likely also plays a major role in the availability of fish for angling in lakes (Skov et al, 2014) and coastal areas (Jepsen et al, 2010). Since cormorants changed their foraging behaviour and started to visit even small streams, some fish populations have declined and the combination of a large otter and heron population with cormorant visits have had negative impacts on especially brown trout, grayling and salmon populations (Jepsen et al, 2014(Jepsen et al, , 2018(Jepsen et al, , 2019. Management/regulation of cormorants has become more active, with several hundred permissions for regulated control of cormorant populations issued annually, including intensive egg-oiling and hunting along rivers in winter, but so far without measurable effect on the level of predation.…”

Section: International Cooperationmentioning

confidence: 99%

Data collection systems and methodologies for the inland fisheries of Europe

Vehanen

Piria

Kubečka

et al. 2020

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The designations employed and the presentation of material in this information product do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations (FAO) concerning the legal or development status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. Dashed lines on maps represent approximate border lines for which there may not yet be full agreement. The mention of specific companies or products of manufacturers, whether or not these have been patented, does not imply that these have been endorsed or recommended by FAO in preference to others of a similar nature that are not mentioned. The views expressed in this information product are those of the author(s) and do not necessarily reflect the views or policies of FAO.

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Change of foraging behavior of cormorants and the effect on river fish

Cited by 28 publications

References 31 publications

The impact of Cormorant predation on Atlantic salmon and Sea trout smolt survival

The impact of Cormorant predation on Atlantic salmon and Sea trout smolt survival

Medium‐term environmental changes influence age‐specific survival estimates in a salmonid population

Data collection systems and methodologies for the inland fisheries of Europe

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