Gezeiteninduziertes Wanderverhaltenvon Fischen (Pisces) in der Mangrove vor Bragranca (Para, Brasilien).

Krumme, Uwe (2000) Gezeiteninduziertes Wanderverhaltenvon Fischen (Pisces) in der Mangrove vor Bragranca (Para, Brasilien). (Diploma thesis), Christian-Albrechts-Universität zu Kiel, Kiel, Germany, 137 pp.

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Abstract

In order to study short- and medium-term changes in the composition of species assemblages in tropical mangrove creeks, weekly day and night sampling was conducted between february and april 1999 (rainy season). For this purpose the mouth of a tidal mangrove creek was closed off at high tide with tapagem nets, and fish and prawns leaving with the ebbing tide were caught. Each tapagem yield was subdivided into consecutive catches. Catch yields ranged between 0.3 kg and 10.3 kg corresponding to minimum and maximum high water level. Mean catch weight during neap tide was 1,9 ± 1,5 kg and 5,7 ± 2,4 kg for spring tides. In total, 41 fish species (26 families) and four shrimp species (2 families) were caught. Important species were Cathorops sp. (Ariidae), Colomesus psittacus (Tetraodontidae), Selenaspis herzbergii (Ariidae), Pseudauchenipterus nodosus (Pseudauchenipteridae), the shrimp Penaeus subtilis (Penaeidae), Anchovia clupeioides (Engraulidae), Mugil spp. (Mugilidae) and Anableps anableps (Anablepidae), accounting for 34, 18, 10, 6, 5, 5, 4 and 4 % of total catch weigth of 66,3 kg. Mean fish biomass was 2,2 ± 1, 1 g/m3 or 1,9 ± 1,3 g/m2. Mean shrimp density was 0,06 ± 0,05 individuals/m3. 87 ± 6 % of the fishes caught were juveniles. Shrimp were mainly juveniles or subadults, indicating that tidal mangrove creek are an important nursery area for these taxa. Shannon-Weaver-diversity H' was low (0,9 ± 0, 1) which is typical for the rainy season period. Eveness J' was lowest at spring tide-night when more rare species entered the creeks and immigration of dominant species was even more severe. This was supported by the species-family ratio indicating highest niche diversity in fish families at spring tide-night. During ebb tide firstly species of the water surface and free water column attempted to leave the tidal mangrove creeks, followed by benthic orientated species as water continued to drain off. Younger fishes left earlier than older ones, whereas young P. subtilis left later than older ones. Feeding was the main reason for entering the mangrove tidal creeks. Some species were present with reproductively active specimens. Male Cathorops sp. were only caught during spring tide, especially at night. Although salinity dropped from 30 to 10 within a month, only abundances of three species (Anchoviella lepidentostole, Chaetodipterus faber und Cynoscion acoupa) increased significantly. Some indicators for reduced predation and realised predator avoidance in the mangrove creeks were found. Fourteen species correlated positive with the maximum water level per tide. This relationship was best described by a power function. According to this, catch yields were most clearly determined by the changes between spring and neap tide. Although less pronounced, constant changes between day and night were noticeable. The composition of the species assemblage in the mangrove tidal creeks, changing with every tide, was significantly determined by the combination of the factors "tide" and "time of day". According to this, four distinct compositions could be distingiushed: spring tide-night, spring tide-day, neap tide-night and neap tide-day. lt seems that maximum water level of a tide, being influenced by wind direction and strength, ultimately determines the actual composition of the species assemblage found in a catch. Neither water temperature nor salinity influenced the composition of the species assemblage as a whole. Considering tide and day/night cycle is recommended for future planning of sampling highly mobile taxa in macrotidal environments.

Document Type: Thesis (Diploma thesis)
Thesis Advisor: Rosenthal, Harald, Saint-Paul, Ulrich and Schories, Dirk
Research affiliation: OceanRep > GEOMAR > FB3 Marine Ecology > FB3-EV Marine Evolutionary Ecology
Refereed: No
Date Deposited: 18 Feb 2008 17:24
Last Modified: 15 Oct 2021 13:23
URI: https://oceanrep.geomar.de/id/eprint/707

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