ABSTRACT-Developmental instability, measured as fluctuating asymmetry (FA; i.e. deviations from perfect bilateral symmetry), was studied using 2 otolith traits (maximum radius and perimeter) in larval anchovies collected during June 1994 dnd June 1995 In the northern Aegean Sea (eastern Mediterrdnean). There was a substantial between-year difference, FA being greater in 1995 than in 1994: mean absolute asymmetry in otolith perimeter was 26.5':;) higher In 1995 than in 1994. Similarly, 3 'growth' relationships (standard length, SL, anal body depth, ABD, and recent otolith growth, ROG, on age, A) and 2 'allon~ctric' oncs (ABD and ROG on SL) were significantly d~fferent between the 2 years and indicated that anchovy larvae collected during 1994 were in better condition than those collected in 1995. These between-year differences could be explained in terms of Lasker's 'stable-ocean hypothesis' Stability of the upper water column was higher in 1994 than in 1995. Subsequently, we examined asymmetry at the level of the individual: using the residuals of the 5 models as indices of condition, cases of significant negative correlation between asymmetry and the residual-based indices were found, a fact which seemed to depend mainly on the otolith trait and the residual variance of the model used to derive the index of condition. These field results suggest that developmental instability, as measured by bilateral asymmetry of the otohths, can be used as an indicator of condition in larval fish

Developmental instability, measured as fluctuating asymmetry (FA) in bilateral traits, has been used widely as an indicator of genetic or environmental stress in a variety of plant and animal taxa. FA arises as small deviations from perfect bilateral symmetry which reflect ‘mistakes’ in developmental processes resulting from the inability of the genotype to buffer itself effectively against environmental perturbations. Recently, it has been proposed that FA in the otoliths can be used as an indicator of condition in larval fish. This paper reviews the conceptual and methodological aspects of FA relevant to its potential use as a measure of well‐being. Its simplicity makes FA an attractive tool to measure developmental precision and condition. However, there are several pitfalls, such as measuring error or potentially size dependence. Subtle asymmetries, i.e. between sides variation of a trait at the individual level, may not always be indicative of condition and should be interpreted with caution. The past‐growth record of otoliths may provide a powerful means of studying the development of asymmetries at the level of the individual.

ABSTRACT. The distribution patterns and feeding habits of 4 deep-water decapod species were investigated from samples collected In experimental trawl surveys carried out along the continental slope of Crete (Eastern Medterranean) in 1994 to 1995, at depths behveen 100 and 1000 m Despite their distnbution overlap, the differences in the distribution patterns of the species along the depth gradient were clear, with Plesionika ensjs and Polycheles typhlops occurring at greater depths than Parapenaeus long~rostns and Plesionika heterocarpus. Stomach content analysis revealed that all species were active predators of benthic invertebrates, while scavenging activity became more important at depths below 500 m. The species exhibited highly diverse diets, but dietary diversity was higher for those inhabiting shallower depths. Ontogenetic dietary shifts were pronounced, although dietary patterns were also significantly affected by season and depth. Interspecific dietary overlap was less than intraspeciflc overlap between size classes and between months. Feeding intensity was associated w t h the distribution patterns of the species and decreased with depth, thus it was significantly lower for the species at the deepest depths, P. typhlopsand P ensis. Dletary patterns of the species e x a m n e d were quite s~milar and differences noted were more consistent with depth-related changes in available food resources than with changes in the position of the species in the food web. Since dietary overlap among the species when they co-occur was high, it is possible that competitive trophic interactions accounted for the low overlap In the bathymetrical distribution of the species examined. Such interactions may be of fundamental unportance on the deep-sea bottoms in the Eastern Mediterranean since environmental parameters such as temperature and salinity are rather constant.

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