The composition and distribution of fish assemblages was examined in a
floodplain lake system in the Amazon basin. Quantitative samples were
collected during the 1992-1993 flooding season at Marchantaria Island, Solimoes
River. A total of 25,819 specimens representing 8 orders, 30 families, 101
genera and 139 species of fish were collected. Analysis of species richness
distribution among 7 vegetation strata showed that vegetated sites had higher
species richness than unvegetated sites. Stands of Paspalum repens had the
most diverse fish fauna. Canonical correspondence analysis (CCA) was used to
investigate relationship between fish assemblages and 16 environmental
variables. CCA revealed that dissolved oxygen, water transparency, water depth
and aquatic vegetation structure were significantly related to fish assemblage
organization. The results suggest that physiological adaptations to hypoxia and
habitat complexity play a major role in the organization of these assemblages.
The morphology, ontogenetic development, shape variability and deposition of
otolith microincrements are described for floodplain serrasalmin fishes.
Serrasalmin otoliths were similar to other ostariophysan, nevertheless their
shape was species-specific. Elliptical Fourier analysis showed that Mylossoma
aureum lapilli were highly variable in shape when compared to closely related
species. PCA and discriminant function analysis indicated that two distinct forms
of lapillus can be recognized for M. aureum, and intra-species variation was
higher than inter-species variation. Otolith microincrement analysis was tested
for these fishes, and microincrement deposition validation showed that Piaractus
brachipomus deposits otolith increments on a daily basis. Patterns of spatial
distribution, growth and mortality characteristics of larvae and juvenile were
examined for M. aureum inhabiting the Marchantaria Island floodplain. Otolith-derived
birth date reconstruction showed that M. aureum spawning season
extended from late November to March, and peak larvae recruitment to the island
occurred in mid-December. Larvae and juveniles had different spatial
distributions in relation to habitat usage. Instantaneous growth coefficients (g)
varied from 0.0197(d�����) to 0.265(d�����) among cohorts. Early-season cohorts had
wider otolith microincrements and higher instantaneous growth coefficients than
late-season cohorts. Mortality estimated by the decline of loge (abundance)
regressed on age indicated that cohort-specific instantaneous mortality varied
significantly among cohorts, ranging from 0.027(d�����) (2.6%/d) to 0.103(d�����)
(9.7%/d). / Graduation date: 2001
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/32616 |
| Date | 25 May 2000 |
| Creators | Petry, Paulo |
| Contributors | Markle, Douglas F. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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