Biomass estimations of common octopus Octopus ...

8 downloads 0 Views 1020KB Size Report
Introduction. • Mexico occupies the third place for the world's highest catches of genus Octopus. • Since 1949, the catch rato of common octopus. Octopus ...
Biomass estimations of common octopus Octopus vulgaris in the continental shelf of Yucatan 1,3

1

2

Otilio Avendaño-Álvarez , Iván Velázquez-Abunader* , Álvaro Hernández-Flores and Alfonso Cuevas-Jiménez

2

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



R2 = 0.36



8000

Catch (tonnes)









6000

● ●



● ●

Figure 3. Diagram of methodology







4000 ● ●

5. Results

● ●



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

22

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



Rio lagartos Dzilam Bravo ●



21

Sisal

6. Conclusions

20

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 (