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Ignoring the spatial structure of the sea cucumber Isostichopus fuscus distribution when granting quotas can be costly

Ignoring the spatial structure of the sea cucumber Isostichopus fuscus distribution when granting quotas can be costly
Ignoring the spatial structure of the sea cucumber Isostichopus fuscus distribution when granting quotas can be costly
There is an increasing demand for fisheries resources worldwide. For example, the Asian markets have traditionally consumed sea cucumber as a delicacy and their buoyant economies have promoted demand for it in recent years. The brown sea cucumber Isostichopus fuscus is the most valuable species from the Eastern Pacific and it has been almost depleted due to overfishing. In this work, we analyzed data of sea cucumber abundance collected monthly (October 2014–December 2016) along the west coast of the Gulf of California (29.95 oN – 28.05 oN) in 1,107 swath (25 × 2 m) quadrats performed at 118 sites with the goal of determining if current fishing quotas are sustainable. We applied a Bayesian hierarchical modelling approach with integrated nested Laplace approximation (INLA) to this data to account for spatial structure in the data when calculating densities. The observed density ranged from a minimum of 0 to a maximum of 0.58 ind/m2, with an average of 0.03 ind/m2 in suitable habitat, defined as the habitat less than 30 m deep and with hard substrate. There are large spatial variations in abundance, but the overall mean suitable habitat is 15.7% (min = 7.8%, max = 28.8%) of the total fishing area. Current quotas are usually higher than 5% of the lower bounds of population density estimates. We propose, among other management measures, that quotas should be granted taking into account the spatial structure of sea cucumber densities as well as the proportion of suitable area within each estate. Given the high levels of illegal fishing within the Gulf of California, it is imperative that quotas are based on the lower bounds of spatially explicit density estimates – along with increased surveillance and enforcement – if the long-term commercial sustainability of the fishery is to be maintained.
0964-5691
1-8
Calderon-Aguilera, Luis E.
0a64df94-4bc2-4766-972f-82368c575ce3
Graham, Laura J.
bc76bad7-f0fd-4e94-acf9-c7450ec36ae2
Eigenbrod, Felix
43efc6ae-b129-45a2-8a34-e489b5f05827
Calderon-Aguilera, Luis E.
0a64df94-4bc2-4766-972f-82368c575ce3
Graham, Laura J.
bc76bad7-f0fd-4e94-acf9-c7450ec36ae2
Eigenbrod, Felix
43efc6ae-b129-45a2-8a34-e489b5f05827

Calderon-Aguilera, Luis E., Graham, Laura J. and Eigenbrod, Felix (2019) Ignoring the spatial structure of the sea cucumber Isostichopus fuscus distribution when granting quotas can be costly. Ocean & Coastal Management, 178, 1-8, [104859]. (doi:10.1016/j.ocecoaman.2019.104859).

Record type: Article

Abstract

There is an increasing demand for fisheries resources worldwide. For example, the Asian markets have traditionally consumed sea cucumber as a delicacy and their buoyant economies have promoted demand for it in recent years. The brown sea cucumber Isostichopus fuscus is the most valuable species from the Eastern Pacific and it has been almost depleted due to overfishing. In this work, we analyzed data of sea cucumber abundance collected monthly (October 2014–December 2016) along the west coast of the Gulf of California (29.95 oN – 28.05 oN) in 1,107 swath (25 × 2 m) quadrats performed at 118 sites with the goal of determining if current fishing quotas are sustainable. We applied a Bayesian hierarchical modelling approach with integrated nested Laplace approximation (INLA) to this data to account for spatial structure in the data when calculating densities. The observed density ranged from a minimum of 0 to a maximum of 0.58 ind/m2, with an average of 0.03 ind/m2 in suitable habitat, defined as the habitat less than 30 m deep and with hard substrate. There are large spatial variations in abundance, but the overall mean suitable habitat is 15.7% (min = 7.8%, max = 28.8%) of the total fishing area. Current quotas are usually higher than 5% of the lower bounds of population density estimates. We propose, among other management measures, that quotas should be granted taking into account the spatial structure of sea cucumber densities as well as the proportion of suitable area within each estate. Given the high levels of illegal fishing within the Gulf of California, it is imperative that quotas are based on the lower bounds of spatially explicit density estimates – along with increased surveillance and enforcement – if the long-term commercial sustainability of the fishery is to be maintained.

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OCMA 2018 764 Calderon MS ver3.1 - Accepted Manuscript
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More information

Accepted/In Press date: 23 June 2019
e-pub ahead of print date: 27 June 2019
Published date: 1 August 2019

Identifiers

Local EPrints ID: 432216
URI: http://eprints.soton.ac.uk/id/eprint/432216
ISSN: 0964-5691
PURE UUID: 934aa24f-d99b-40ce-a636-693311e1cfa7
ORCID for Felix Eigenbrod: ORCID iD orcid.org/0000-0001-8982-824X

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Date deposited: 04 Jul 2019 16:30
Last modified: 07 Oct 2020 06:01

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