Colonization of the deep sea by fishes.
Bottom Line: Analysis of maximum depth of occurrence of 11 952 marine fish species shows a global decrease in species number (N) with depth (x; m): log10 N = -0·000422x + 3·610000 (r(2) = 0·948).The slopes for the Classes Myxini (-0·000488) and Actinopterygii (-0·000413) follow this trend but Chondrichthyes decrease more rapidly (-0·000731) implying deficiency in ability to colonize the deep sea.Deep-sea invasive families such as Ophidiidae and Liparidae make the greatest contribution to fish fauna at depths >6000 m.
Affiliation: Oceanlab, Institute of Biological and Environmental Sciences, University of Aberdeen, Main Street, Newburgh, Aberdeen AB41 6AA, U.K.Show MeSH
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Mentions: The depth frequency distributions of the 31 deep-sea families are shown in Fig. 6. Regression equations of the form log10N = mx + k, have been fitted to the distributions, where N is the number of species within the depth interval, m is the slope (rate of change in species number with depth), k is a constant (log10 number of species at zero depth) and x is depth (m). These values for each family are given in Table2. Families such as the Liparidae (166) with slope values <−0·0003 and r2 > 0·8 have maximum species numbers at shallow depths and a good fit to the general model of logarithmic decrease in species number with depth. These can be regarded as deep-sea invasive families. Families such as the alepocephalids (39) with a peak in numbers at depths below 1000 m show a poor fit to the model and have slope values that are positive (Linophrynidae, 91) or >−0·0001. These can be regarded as deep-sea endemic families that have either lost their presumed shallow-dwelling family members through extinction or have simply diverged so much from their shallow-water ancestors as to form a new family. Examining r2 and slope values in Table2, it is evident that all the three divisions of teleosts, lower, Paracanthopterygii and Acanthopterygii, contribute families across the spectrum between invasive and endemic. Correlations between family number and slope and r2 in Table2 are both insignificant (r2 = 0·0046 and 0·0259, respectively) indicating that taxonomic position is no predictor of whether a deep-sea family is endemic or invasive. For several of the families designated as invasive by this analysis, in Macrouridae, Stomiidae and Myctophidae, the peak of distribution of maximum depths lies at continental slope or mesopelagic depths of 500–1000 m rather than between the surface and 500 m.
Affiliation: Oceanlab, Institute of Biological and Environmental Sciences, University of Aberdeen, Main Street, Newburgh, Aberdeen AB41 6AA, U.K.