Abundance‐depth relationship, condition factor and adaptive value of zooplanktophagy for red bandfish, Cepola macrophthalma

Abstract

The abundance‐depth relationship, condition factor and feeding of red bandfish, Cepola macrophthalma, were studied from trawl samples collected seasonally in 1986–1988 in the western Aegean Sea (Greece). The red bandfish comprised numerically 1.4% of the total fish catch. Its abundance ranged between 0 and 1362 individuals/h (mean = 57.7 individuals/h, +s.d.= 124.7). The relationship between the natural logarithm of the mean number of individuals/h, ln[(n/h) + 1], and depth, D in m, was found to be described by the following quadratic model: image Feeding intensity and condition factor were significantly (P <0.05) lower in December and March, when annuli formation takes place, and significantly higher (<0.05) in June and/or September when reproduction takes place. The red bandfish is a zooplankton predator. Copepods and euphausids dominated by far its diet and made up 60.4% and 31.1 % by number, respectively. The remainder of the diet was shared by cladocerans, decapods, mysids, chaetognaths, amphipods, fish larvae and decapod larvae. Red bandfish has probably evolved a zooplanktophagus habitat because, by providing a relatively abundant food supply, it will neither limit its high linear growth in the first 4–5 years of life nor increase its predatory induced mortality.