Cryptic diversity and limited connectivity in octopuses: Recommendations for fisheries management

Abstract

The market demand for octopus grows each year, but landings are decreasing, and prices are rising. The present study investigated (1) diversity of Octopodidae in the Western Indian Ocean (WIO) and (2) connectivity and genetic structure of Octopus cyanea and O . vulgaris populations in order to obtain baseline data for management plans. A fragment of the cytochrome C oxidase subunit 1 (COI) gene was sequenced in 275 octopus individuals from Madagascar, Kenya and Tanzania. In addition, 41 sequences of O . vulgaris from South Africa, Brazil, Amsterdam Island, Tristan da Cunha, Senegal and Galicia were retrieved from databases and included in this study. Five different species were identified using DNA barcoding, with first records for O . oliveri and Callistoctopus luteus in the WIO. For O . cyanea (n = 229, 563 bp), 22 haplotypes were found, forming one haplogroup. AMOVA revealed shallow but significant genetic population structure among all sites (ϕ ST = 0.025, p = 0.02), with significant differentiation among: (1) Kanamai, (2) southern Kenya, Tanzania, North and West Madagascar, (3) Southwest Madagascar and (4) East Madagascar (ϕ CT = 0.035, p = 0.017). For O . vulgaris (n = 71, 482 bp), 15 haplotypes were identified, forming three haplogroups. A significant genetic population structure was found among all sites (ϕ ST = 0.82, p ≤ 0.01). Based on pairwise ϕ ST -values and hierarchical AMOVAs, populations of O . vulgaris could be grouped as follows: (1) Brazil, (2) Madagascar and (3) all other sites. A significant increase in genetic distance with increasing geographic distance was found (Z = 232443, 81 r = 0.36, p = 0.039). These results indicate that for O . cyanea four regions should be considered as separate management units in the WIO. The very divergent haplogroups in O . vulgaris from Brazil and Madagascar might be evolving towards speciation and therefore should be considered as separate species in FAO statistics.

Potential biomass and distribution of octopus in the eastern part of the Campeche Bank (Yucatán, Mexico)

“…Since some of these catches are never properly identified, they are commonly reported as Octopus vulgaris. Due to the new findings in octopus taxonomy (Norman et al 2014, Amor et al 2017, Van Nieuwenhove et al 2019), all landings reported under that name should be reviewed (e.g. Solís-Ramírez 1994, Norman et al 2014, Emery et al 2016.…”

Phylogeography of the insular populations of common octopus, Octopus vulgaris Cuvier, 1797, in the Atlantic Macaronesia

“…Additional haplotypes not sampled in the present work were apparent in the entire COX1 data set (including GenBank sequences), suggesting a deep coalescence dating within the MIS 5 interglacial. Haplogroup α was also detected from COX1 data from the southern Atlantic (Tristan da Cunha, Amsterdam Island and South Africa), and southwestern Indian ocean (Madagascar) [73], reinforcing a wide, southern distribution, and ancestral origin.…”

Characterization of Some Commercially Important Octopus (Mollusca: Cephalopoda) from Indonesian Waters using Mitochondrial DNA Cytochrome Oxidase Sub-Unit I (Mt-DNA COI)

“…At present, octopus caught to be used in export commodity was harvested from around 90 countries (Sauer et al, 2019) including Indonesia. Every year the global export demand for octopus continues to increase, but landings are decreasing and therefore the prices continue to increase (Nieuwenhove et al, 2019). This kind of shellfish is captured from nature in various ways, such as the use of trawls (Melis et al, 2018), traps (Sobrino et al, 2011), spear guns (Sauer et al, 2011;Benbow et al, 2014) or metal spears or sticks are also used by traditional fishermen in Hawaii, Tonga, Tokelau (Amstrong et al, 2011;Tiraa-Passfiled, 1999) and in Karimunjawa (this study).…”

“…The continued capture of large numbers of octopuses without the correct identification of the species allows for the accidental overexploitation of certain species. This overexploitation can lead to the extinction of this species (Nieuwenhove et al, 2019), although this may also occur due to several factors such as parasites and pathogens (Rowley et al, 2014), pollution, exploitation and climate change (Gimenez, 2019).…”