. Boletin de la Sociedad de BiologÃ-a de Concepción. Sociedad de BiologÃ-a de Concepción; Biology; Biology. Bol. Soa BioL Concepción. Chile. Tomo 62, 1991 \ é a a ^.^--Ã-^ E I--"^ ^\v T X â¢1 â a ^ '-^- \ i k- ,*"'â c ,' _a / 'â 5 / o 2 iÃ--'-'- 1 / '''' i Sp Su Stasons rlOO 50. Vi Sp Su Au Sessons FiG. 2. Seasonal relations among Diplodon chilensis chilensis condition Ã-ndex, substraÃ-a organic matter and organic particles in suspensión at sandy (a) and muddy (b) environments. () standard deviation in horizontal segments. that the highest valúes are registered in muddy ár
. Boletin de la Sociedad de BiologÃ-a de Concepción. Sociedad de BiologÃ-a de Concepción; Biology; Biology. Bol. Soa BioL Concepción. Chile. Tomo 62, 1991 \ é a a ^.^--Ã-^ E I--"^ ^\v T X â¢1 â a ^ '-^- \ i k- ,*"'â c ,' _a / 'â 5 / o 2 iÃ--'-'- 1 / '''' i Sp Su Stasons rlOO 50. Vi Sp Su Au Sessons FiG. 2. Seasonal relations among Diplodon chilensis chilensis condition Ã-ndex, substraÃ-a organic matter and organic particles in suspensión at sandy (a) and muddy (b) environments. () standard deviation in horizontal segments. that the highest valúes are registered in muddy áreas although these valúes vary significantly during the year (Table 3).In sandy bottoms, on the contrary, density is relatively stable all the year round, though the valúes obtained are significantly lower than those obtained in muddy substrate. The amount of organic matter attached to the substrate's particles is higher in muddy bottoms with annual variations of 15,63 and 25,69% for muddy bottoms in winter and summer, respectively and 13,37 and 18,40% for sandy substrata in the same seasons. All differences recorded are significant only during the summer (Table 4). Water-suspended solid particles, either organic or inorganic, do not show a definite trend in both environments even though the organic particles are always higher in muddy substrate. These differences are significant only in winter and summer (Table 5). DISCUSSION AND CONCLUSIONS The condition index is a parameter that has been widely used in studies of the reproductive cycles of aquatic species to show that the chan- ges in the fat condition of individuáis are due to reproductive processes. Nonetheless, few studies have related this state (condition index) to popu- lation characteristics such as density and availa- bility of existing resources for the populations in different kinds of substrata. Table 2. Seasonal regression equations between valve dry weight (VDW) and valve lenght
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