Biomass estimations of common octopus Octopus vulgaris in the continental shelf of Yucatan 1,3
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2
Otilio Avendaño-Álvarez , Iván Velázquez-Abunader* , Álvaro Hernández-Flores and Alfonso Cuevas-Jiménez
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1
Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Unidad Mérida | 2 Universidad Marista de Mérida, Yucatán | 3 Universidad de Ciencias y Artes de Chiapas, Tonalá, Chiapas. *e-mail:
[email protected]
1. Introduction
4. Methods
• Mexico occupies the third place for the world’s highest catches of genus Octopus.
Biomass for common octopus Octopus vulgaris were estimated through three methods. The methods used were: Swept Area method [1], Stratified method [2] and Geostatistical method [3] (Figure 3).
• Since 1949, the catch rato of common octopus Octopus vulgaris has peaked from 5,000 tons to 10,000 tons in 2014 (Figure 1). • The rate of exploitation and the status of the stocks across the different regions in Mexico, is less known. • The present study aims to estimate, for the first time, the common octopus’ biomass, abundance and distribution on the continental shelf of Yucatan
Cruises
Four: May 2016, July 2016, December 2016, January 2017, from 27 to 30 sampled stations
Data
Total catch (Number of organisms and total weight), Swept area, longitude and latitude
Biomass
Methods: Swept Area, Stratified, Geostatistical
Results
Biomass and Density
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R2 = 0.36
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8000
Catch (tonnes)
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6000
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Figure 3. Diagram of methodology
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4000 ● ●
5. Results
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2005
2010
2015
year
Figure 1. Catches of common octopus Octopus vulgaris in Yucatan, Mexico
2. Objective
Estimated biomass Bt showed variation in all three methods. The three methods agreed that the highest biomass occurred in December (Bt > 200 t) but with low densities, suggesting a recruitment period in early autumn. The results showed that the biomass peak could occur in the middle of the octopus fishing season (August-December) (Figure 4). Method
To determine the available biomass of common octopus, Octopus vulgaris, in the northeastern región of the Campeche Bank, throught the application of tree statistical models (Swept Areas, Stratified, Geostatistics).
Biomass was estimated through of four cruises were performed from 2016 to 2017. The number of stations per cruise varied from 27 to 30 (Figure 2).
Stratified
Method
Swept area
A)
Geostatistic
Stratified
Swept area
B) 30
300
Biomass X 10000 km2
3. Study Area
Geostatistic
Organisms km2
2000
200
20
100
10
0
0
24 N
23
W
May
E
July
December
January
May
Month S
July
December
January
Month
Study Area
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Figure 4. A) Estimated biomass of common octopus Octopus vulgaris at the continental shelf of Yucatan and B) Estimated densities of common octopus Octopus vulgaris at the continental shelf of Yucatan
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Rio lagartos Dzilam Bravo ●
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Sisal
6. Conclusions
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19 0
100 kilometers
200
18 −92
−91
−90
−89
−88
−87
−86
The low variability in potential biomass between models can be explained by the difference in the statistical assumptions on the distribution of the abundance (regionalized and homogeneous). Abundances were higher during July and December than in May and January, where abundances were lower (>20 org/km2), probably to the end of recruitment period. Unlike than in May and January, where abundances were lower in May and January (
