The Effects of Habitat Fragmentation on Fish Developmental Stability

In nature, organisms exist in less than ideal conditions making stress a constant factor throughout their life. These stressful environments may disturb developmental processes, causing long-term, detrimental changes to an organism expressed as bilateral variation in morphology or fluctuating asymmetry (FA). Fluctuating asymmetry has been shown to be associated with accidents during morphogenesis due to environmental factors and hence is considered a measure of developmental instability. One environmental stressor that may affect aquatic organisms is stream habitat fragmentation. Stream habitat fragmentation is the lack of connectivity between upstream and downstream populations or sites. Stream fragmentation can create distinct patches of varying habitat quality within a stream. The deterioration of habitat quality associated with increased levels of habitat fragmentation may bring about abiotic changes that act as stressors, which can cause a disruption in an organism\u27s developmental processes leading to fluctuating asymmetry. Therefore, fluctuating asymmetry was examined in respect to habitat fragmentation to determine if: 1) abiotic factors differ between sites with differing habitat quality, 2) fluctuating asymmetry values of fish differed between sites of varying habitat quality and 3) fluctuating asymmetry values could be used as an indicator of stream integrity. To examine the effects of habitat fragmentation on fluctuating asymmetry eight sites were chosen along Polecat Creek, a fourth order tributary associated with the Embarras River near Charleston, Illinois. Sites were classified by habitat quality using the Stream Habitat Assessment Procedure (SHAP) developed by the Illinois Environmental Protection Agency (IEPA, 1994). Average SHAP scores ranged from a low of 57 to a high of 147 for the eight sites sampled. An analysis of variance revealed a significant difference in mean SHAP scores among the eight sites sampled (P \u3c 0.01). A Tukey\u27s test (mean comparison test) was then performed to determine where the differences were among the eight sites. The outcome of the Tukey\u27s test was that the eight sites were grouped into two habitat quality categories, good or poor. Poor categories are usually associated with abiotic factors such as increased siltation, highly variable water temperatures, decreased dissolved oxygen levels, increased pollutants and stream desiccation. While the good category has less variable water temperatures, higher dissolved oxygen levels, and minimal to no siltation. To ascertain whether fluctuating asymmetry values increase with the amount of habitat fragmentation or change in habitat quality, two abundant Illinois fish, the common stoneroller (Campostoma anomalum) and the striped shiner (Notropis chrysocephalus) were collected from the eight sites along Polecat Creek. The 217 common stonerollers and 136 striped shiners collected form Polecat Creek each were landmarked for 11 and 13 points, respectively, and analyzed using the procrustes method of shape analysis. Shape analysis revealed that fluctuating asymmetry (FA) values observed for both species were not significantly different (P \u3e 0.1) between habitat quality categories. To expand the analysis and correct for individual measurement error and to allow for comparisons among sites, we employed the use of a best linear unbiased predictor (BLUP). When accompanied by a BLUP analysis, the fluctuating asymmetry values for both species were significant (P\u3c 0.0001) among all eight sites. A Bonferroni test indicated that sites 2 and 7 (both good sites) had significantly lower BLUP FA values than the other six sites for the common stoneroller. While a regression analysis revealed no significant relations between mean SHAP score and BLUP FA value (df= 6, F = 0.04, P \u3c 0.85). Whereas the stripe shiner\u27s Bonferrini test illustrated that site 1 (good site) and 5 (poor site) had significantly higher FA values (P \u3c 0.05) as compared to the other sites. Similarly, a regression analysis for the stripe shiners indicated no significant relationship between mean SHAP score and BLUP FA value (df= 4, F = 1.72, P \u3c 0.29). This study does not show that fluctuating asymmetry is associated with habitat fragmentation and there is still some controversy over the use of fluctuating asymmetry. Thus, abiotic factors, such as dissolved oxygen, water temperature, and sedimentation, associated with habitat fragmentation may not be major stressors that cause a disruption in growth and morphology of an organism. Therefore, fish species may view their habitat in a different manner than we would be lead to believe and that perhaps other abiotic factors of the stream may have a more adverse affect upon the organism