Does Pond Water Reflectance Influence Double-crested Cormorant Selection of Aquaculture Ponds?

Double-crested cormorants, Phalacrocorax auritus, are a frequent and major avian predator on channel catfish, Ictalurus punctatus, and other aquaculture species throughout the southeastern USA. Although cormorant movements and occurrence within the aquaculture production region are understood, no studies have focused on the mechanisms utilized by these avian predators to select foraging sites within these high-density aquaculture systems. The objective of this study was to determine if cormorant abundance is associated with specific (ultraviolet to visible) light reflectance spectra within commercial catfish ponds. Three commercial farms were used in this study; each farm had four ponds classified as "preferred" and another four ponds classified as "avoided" based on observing cormorant numbers for 3 mo prior to reflectance measures (>100 h observation for each pond). Reflectance and pond turbidity were measured weekly for 7 wk during the period of maximal over-wintering cormorant numbers. Water samples were collected at the surface (1 cm depth) and secchi depth (10-41 cm) at two locations (upwind and downwind sides) within each pond to determine spectral reflectance and turbidity. Average pond reflectance values were not significantly different between ponds preferred and avoided by cormorants; however, upwind reflectance significantly differed from downwind reflectance between cormorant use groups. Using cross-validation discriminant analysis, the accuracy of separating upwind ponds preferred and avoided by cormorants was over 62%. Repeated measures ANOVA identified the reflectance at 370, 380, 460, 500, 510, and 620 nm as significantly different between ponds preferred and avoided by cormorants. The lower wavelengths (380-410 nm) correspond to known UV-A sensing compounds in cormorants and the other wavelengths share characteristics associated with algal biomass. Cormorants utilize ponds that have lower algal biomass when compared with avoided ponds.

[1]  M. Théry,et al.  Avian Color Vision and Coloration: Multidisciplinary Evolutionary Biology , 2007, The American Naturalist.

[2]  A. R. Stickley,et al.  Impact of Double‐Crested Cormorant Depredations on Channel Catfish Farms , 1992 .

[3]  P. Butler,et al.  Vision and Foraging in Cormorants: More like Herons than Hawks? , 2007, PloS one.

[4]  G. Katzir,et al.  Prey detection by great cormorant (Phalacrocorax carbo sinensis) in clear and in turbid water , 2008, Journal of Experimental Biology.

[5]  Martin Stevens,et al.  The unsuitability of html-based colour charts for estimating animal colours – a comment on Berggren and Merilä (2004) , 2005, Frontiers in Zoology.

[6]  G. Katzir,et al.  Corneal power and underwater accommodation in great cormorants (Phalacrocorax carbo sinensis) , 2003, Journal of Experimental Biology.

[7]  A. Wywialowski.  Wildlife-Caused Losses for Producers of Channel Catfish Ictalurus punctatus in 1996 , 1999 .

[8]  G. Katzir,et al.  Cormorants keep their power: visual resolution in a pursuit-diving bird under amphibious and turbid conditions , 2004, Current Biology.

[9]  E. Korpimäki,et al.  Ultraviolet vision and foraging in terrestrial vertebrates , 2002 .

[10]  M. Pavlicev,et al.  UV reflecting vole scent marks attract a passerine, the great grey shrike Lanius excubitor , 2002 .

[11]  J. F. Glahn,et al.  The Impact of Double-Crested Cormorants on the Mississippi Delta Catfish Industry: A Bioenergetics Model , 1995 .

[12]  O. Håstad,et al.  Different Ranking of Avian Colors Predicted by Modeling of Retinal Function in Humans and Birds , 2008, The American Naturalist.

[13]  J. Viitala,et al.  Attraction of kestrels to vole scent marks visible in ultraviolet light , 1995, Nature.

[14]  N. Hart.  Variations in cone photoreceptor abundance and the visual ecology of birds , 2001, Journal of Comparative Physiology A.

[15]  J. Viitala,et al.  Behavioural evidence for ultraviolet vision in a tetraonid species – foraging experiment with black grouse Tetrao tetrix , 2002 .

[16]  Jules Davidoff,et al.  Color perception , 1998 .

[17]  Anatoly A. Gitelson,et al.  Remote estimation of chlorophyll concentration in hyper-eutrophic aquatic systems: Model tuning and accuracy optimization , 2006 .

[18]  J. Lythgoe.  The Ecology of vision , 1979 .

[19]  I. Cuthill,et al.  Plumage Reflectance and the Objective Assessment of Avian Sexual Dichromatism , 1999, The American Naturalist.

[20]  J. Viitala,et al.  Ultraviolet reflection of berries attracts foraging birds. A laboratory study with redwings (Turdus iliacus) and bilberries (Vaccinium myrtillus) , 1999, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[21]  H. Schramm,et al.  Depredation of Channel Catfish By Florida Double‐Crested Cormorants , 1984 .

[22]  I. Cuthill,et al.  Does Lepidopteran Larval Crypsis Extend into the Ultraviolet? , 1998, Naturwissenschaften.

[23]  M. Vorobyev,et al.  Colour vision of domestic chicks. , 1999, The Journal of experimental biology.

[24]  Livia S. Carvalho,et al.  The molecular evolution of avian ultraviolet- and violet-sensitive visual pigments. , 2007, Molecular biology and evolution.