Fluctuating asymmetry and exogenous stress in fishes: a review

Abstract

Fluctuating asymmetry (FA), which has been examined in a variety of plants and animals, is widely promoted as a useful bioindicator of exogenous stressors in habitats, whether of natural or anthropogenic origin. Wildlife managers and researchers often use a specific group of organisms as an indicator of the health of a given habitat. The purpose of this review is to demonstrate that FA can be an effective fish biomonitoring tool by presenting a vote counting meta-analysis of 81 fish FA studies published between 1966 and the first half of 2009. The vote counts were analyzed with the G test for independence to determine whether the probability of observing significant morphological asymmetry is determined by character type, exogenous stressor type, or fish order. The information obtained from these papers and their analysis is then used to outline areas in which FA studies can be improved: (1) carefully considering character choice; (2) distinguishing between asymmetry types; (3) determining the level of measurement error in between-sides character variation; (4) determining baseline FA levels in populations; (5) increasing the number of laboratory studies which corroborate field observations of FA; (6) conducting true replications of studies to validate previous findings. Only with more critical experimental design and data analysis can FA be used as a powerful tool for assessing environmental degradation.

Evaluating Morphological Asymmetry in Three Species of the Genus <i>Hydrocynus</i> from the White Nile in Sudan

“…However, water chemistry may have a more direct influence on FA and may be a more powerful predictor of developmental stress. Other factors such as nutrition, chemical contaminants and pH have also been shown to increase FA (Allenbach, 2011). Annual variability in temperature and water levels could also impact a variety of stressors contributing to increase variability among individuals.…”

Fluctuating Asymmetry in Two Common Freshwater Fishes as a Biological Indicator of Urbanization and Environmental Stress within the Middle Chattahoochee Watershed

“…We selected and quantified five paired bilateral characters (Figure 4) that are dichotomous and conserved between Lepomis species [27]. Preliminary results showed no significant responses and almost no variability in the FA of meristic characters among creeks.…”

“…Metric characters were measured to the nearest ±0.01 mm in triplicate on three different days allowing for assessment of measurement error (ME) [4]. [27] were selected and quantified. Meristic characters: (1) pored lateral line scales; and (2) pelvic fin rays were not used in analyses.…”

“…Additionally, Tull and Brussard acknowledged the importance of finding effective methods for identifying stress on wildlife population to help indicate early signs of potential population declines [16]. Researchers (e.g., [1,[25][26][27]) have therefore used FA as an indicator of anthropogenic stressors and how these anthropogenic based stressors effect developmental stability of fishes in resident communities.…”

Fluctuating and Directional Asymmetry of the Blue Mussel (Mytilus edulis): Improving Methods of Morphological Analysis to Explore Species Performance at the Northern Border of Its Range

“…FA has generated interest among population biologists because it reflects one of the components of fitness-developmental stability, i.e., the ability of an organism to consistently produce an "ideal" phenotype in a given environment [5]. Although an association between FA and fitness is not always observed in empirical studies, recent reviews concluded that, overall, FA can be considered a useful tool for assessing a population's average fitness [6][7][8].…”