Banca de DEFESA: Kessin Ângelo Guimarães Cabral

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : Kessin Ângelo Guimarães Cabral
DATE: 04/12/2023
TIME: 14:00
LOCAL: Universidade Federal de São João del-Rei - Campus Dom Bosco
TITLE:

Applicability of stereo-BRUV to estimate the size structure of Oligosarcus paranensis in the Mangue stream located in the Serra de São José

KEY WORDS:

Stream, Stereo-BRUV, Estimate the Size, VidSync

PAGES: 30
BIG AREA: Ciências Biológicas
AREA: Ecologia
SUMMARY:

The efficiency of data collection depends on the association between methodology and
objectives. Methodologies can be of various types and may or may not require researcher
involvement. In the field of ichthyology, especially in the realm of stream fish, there are
numerous methods for collecting ecological information. One notable methodology is the
BRUV (Baited Remote Underwater Video), which involves remote underwater video sampling
using bait to attract fish into the camera's field of view. While it is a versatile methodology,
extracting biometric information from video footage poses a significant challenge, particularly
regarding size structure data of the filmed fish. Several proposals have been employed to
enhance the extraction of size data, such as the use of specific configurations within the BRUV
setup. One of these configurations involves the use of two cameras, known as stereo-BRUV,
which requires calibration processes involving relatively expensive software or less expensive
software but with a higher level of computational expertise. A recently emerged software has
shown viability for such calibration and demonstrated efficiency in estimating fish sizes, as well
as ecological data like species richness and abundance. One of the species requiring more
detailed ecological data extraction is Oligosarcus paranensis, a species with a recognized
distribution in the Mangue stream, within the Serra de São José. Consequently, the objective of
this study was to assess the applicability of using stereo-BRUV for estimating the sizes of O.
paranensis. To verify the software's functionality, 15 model fish were created in a laboratory,
spanning sizes from 23.4mm to 148.3mm, measured with calipers and defined as the actual sizes.
Each model fish was measured five times using stereo-BRUV, totaling 75 measurements. There
was no statistical difference between the data, with an average absolute error of 2.3%. In the
comparison of size structure, the comparison was made between the fish sizes obtained using
the software and those captured with traps. Thirty 30-minute videos were collected at five points
in the Mangue stream, with the stereo-BRUV structure deployed first for sampling, immediately
followed by the traps. The mean and standard deviation of size between the capture methodology
were 50.9mm ± 18.4mm, while for the individuals filmed, it was 60.3mm ± 17.2mm. There was
sufficient evidence to suggest a statistical difference between the measurements. Smaller fish
were more frequently captured in the traps, while larger fish appeared more often in the videos.
Regarding the sampling points, the Mann-Whitney test showed differences between points 1, 2,
and 3, which had statistically different size data compared to the fish sizes found at points 4 and
5. There was no difference between points 1, 2, and 3, and points 4 and 5. In terms of abundance,
the videos recorded a total of 155 fish with an average of 5.1 fish, whereas the captured fish
numbered 378 with an average of 12.6. At the sampled points 1, 2, 3, 4, and 5, the average
number of individuals in the videos was 5.8, 7.8, 3.8, 4.3, and 4.0, respectively, while for the
captures, the averages were 5.8, 8.1, 2.1, 27.8, and 19.0. Through the use of stereo-BRUV, a
new parameter for assessing abundance was introduced, considering the maximum number of
individuals viewed and identified in a short video segment (NMAX), added to other fish whose
sizes were not already evident in the NMAX, referred to as NMAX+. NMAX+ improved
abundance estimates by an average of 60%. However, concerning size estimation, there was not
a statistically significant difference for the size structure estimate. In terms of antagonistic
behavior among O. paranensis individuals, 46 events were observed during all the videos. There
was a statistical difference between the sizes of fish that initiated attacks on those that fled. The
correlation between the data showed a 50 percent size association, indicating that not only larger
fish attacked smaller ones, but reversed cases were also identified by stereo-BRUV. The use of
the stereo-BRUV methodology proved to be efficient in estimating fish size. It can be applied
in stream environments and is highly recommended for conservation areas. Furthermore, the
methodology can be employed in various other studies involving size and distance estimation,
offering excellent precision in the results.

BANKING MEMBERS:
Presidente - 1626222 - ANDREY LEONARDO FAGUNDES DE CASTRO
Interno - 1804372 - FERNANDO CESAR CASCELLI DE AZEVEDO
Externo à Instituição - LUIZ GUSTAVO MARTINS DA SILVA
Externo à Instituição - RICARDO MACEDO CORRÊA E CASTRO - USP