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Fish  assemblages  in  sicilian  areas  invaded  by  �aulerpa  spp.      589

            At  each  of  the  three  above  mentioned  locations  we  performed  three  censuses,  at
            3-5  m  depth  range,  for  a  total  of  27  underwater  surveys.  These  locations  con-
            sisted of a soft bottom covered mainly by a continuous meadow of Caulerpa spp.
                                                                      -2
            (average  of  upright  fronds  ±  standard  deviation  450  ±  130  m )  with  patches  of
            posidonia oceanica (L.). Data were analysed by non-metric multidimensional scal-
            ing  (nMDS),  using  Bray-�urtis  distance  index  on  untransformed  data.  We  used
            analysis of similarity (ANOSIM) to examine differences among Caulerpa beds in
            each of the three sampling times (PRIMER, 6.1, Plymouth Marine Laboratory).


            Results
               A  total  of  28  fish  species,  representing  8  families,  for  a  total  of  1298  indivi-
            duals,  were  recorded.  The  most  frequent  species  at  all  locations  were  Coris  julis
            (Linneo 1758) (14±2.3 SE), symphodus tinca (Linneo 1758) (7.3±1.8 SE), oblada
            melanura  (Linneo  1758)  (5.7±3.6  SE),  diplodus  vulgaris  (E.  Geoffroy  St.  Hilaire
                   This study was funded by the M.A.T.T. (Ministero dell’Ambiente e Difesa del Territorio) research project to GRE
            1817) (4.6±0.6 SE) e diplodus sargus (Linneo 1758) (4.0±0.49 SE). Species richness
                   (Gruppi Ricerca Ecologica).
            and eveness were not conspicuously high at any Caulerpa bed, but the fish assem-
            blage observed in June on C. taxifolia showed the highest diversity and evenness
            values, 2.08 and 0.90 respectively, than in those collected on C. racemosa and �.
            prolifera. The nMDS ordination (Fig. 1) showed that fish assemblages present on
                   Fig. 1 - nMDS ordination of fish assemblages from the locations affected by C. prolifera (Pro), C. taxifolia (Tax)
            C. taxifolia, C. racemosa and C. prolifera constituted two distinct groups. Accor-
                   and C. racemosa (Rac) sampled in June (G), July (L) and August (A) 2004.
                   Ordinamento nMDS dei popolamenti ittici presenti nelle tre località colonizzate da C. prolifera (Pro), C. taxifolia
            ding  to  ANOSIM  test,  the  fish  assemblage  of  the  site  colonized  by  C.  taxifolia
                   (Tax) e C. racemosa (Rac) campionate a giugno (G), luglio (L) ed agosto (A) 2004.
            significantly differed from those covered by C. racemosa and C. prolifera (Global
            R= 0.6, significance level %=0.1; pairwise tests: C. tax vs C. prol **; C. tax vs C.
            rac ** and C. rac vs C. prol*).

                                                           Stress: 0.14
                                                                          ProG   Pro L


                                                                         Pro A   Tax G


                                                                         Tax L   Tax A


                                                                         Rac G   RAc L


                                                                          Rac A





            Fig.  1  -   nMDS ordination of fish assemblages from the locations affected by C. prolifera (Pro),
                   C.  taxifolia  (Tax)  and  C.  racemosa  (Rac)  sampled  in  June  (G),  July  (L)  and  August
                   (A) 2004.
                   ordinamento nMds dei popolamenti ittici presenti nelle tre località colonizzate da �. prolifera (pro),
                   �. taxifolia (tax) e �. racemosa (rac) campionate a giugno (G), luglio (l) ed agosto (a) 2004.
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