Jorge Hernández-Urcera

The African seahorse Hippocampus algiricus has been considered restricted to the eastern Atlantic coast of Africa, with occasional records in Macaronesian archipelagos. The species is currently classified as Vulnerable by the International Union for Conservation of Nature (IUCN). Here, we report the first confirmed occurrence of this species in the Mediterranean Sea, based on photographic and video evidence. The specimen was identified using diagnostic morphological characters and morphometric analysis. This record represents a north‐eastern range extension and aligns with ongoing tropicalization processes in the western Mediterranean driven by rising sea temperatures.

Reproductive behaviour in octopuses is diverse, yet field observations remain limited for nocturnal species such as Callistoctopus macropus . We report the first documented case of intertidal emergence during copulation in an octopus. During a night dive in Ibiza, a mating pair of C. macropus moved gradually from shallow water onto the rocky shore while remaining physically connected. Once emerged, the female showed a putative escape behaviour, anchoring to nearby rocks, while the male persisted and counter‐anchored, resulting in a prolonged struggle with both individuals partially exposed for ~20 min before re‐submerging. This behaviour is unprecedented and suggests that intertidal emergence may function as an extreme female resistance tactic within the context of sexual conflict. These observations expand the known behavioural repertoire of octopuses and highlight the need for further study of social dynamics in natural settings.

Octopuses are a vital global fisheries resource for both food and economic security, and rising demand is putting increasing pressure on their populations in many regions, making conservation measures essential. Four overarching conservation methods were identified: area closures, gear regulations, effort regulations and landing regulations, with evidence reviewed from Europe, Africa, Latin America, Asia and Australia. The feasibility and ethics of octopus aquaculture are also discussed. Regional adaptations are necessary, as no universal strategy fits all octopus species in all areas, and promoting citizen science and using fisher knowledge can help fill knowledge gaps. Co‐management strategies show promise in addressing small‐scale fisheries management challenges. Insights gathered in this review will assist managers and stakeholders in establishing regulations and conservation initiatives aimed at enhancing the productivity and sustainability of fisheries that interact with octopuses. Additionally, it identifies knowledge gaps that require further attention.

The early life stages of Octopus vulgaris face significant challenges in sandy environments, where shelter is limited and predation risk is high. This study examines how juvenile octopuses adapt to these conditions, focusing on their use of empty bivalve shells as shelters. Between May 2022 and June 2023, through four SCUBA diving expeditions in the Cíes Islands, NW Spain, nine juvenile octopuses were found inhabiting bivalve shells. The juveniles preferentially selected shells that fit their body size, providing protection and minimizing exposure. They manipulated the shells for security and positioned themselves strategically for optimal visual surveillance. Additionally, they used camouflage techniques, blending with the sandy substrate. When threatened, some octopuses displayed bipedal locomotion to enhance their escape. This study highlights the adaptive flexibility of juvenile O. vulgaris in response to predation pressures in sandy habitats, adding to the growing but limited knowledge of habitat‐specific behaviors that can help contribute to the conservation strategies of wild populations.

Anatomical abnormalities in octopuses, whose behavior is facilitated by flexible, neuron-rich arms, offer insights into life histories and the neurological implications of understudied conditions such as bifurcation. Although documentation is scarce, here we present in situ videos of nine-armed O. vulgaris with a functional bifurcated R1 arm. Analysis using RDAs and GLMs investigated the impact of the bifurcated arm on behavior and examined changes during growth. Analysis revealed a differential usage of between the bifurcated arms in addition to an initial specialization of the bifurcated arms for actions below the body, decreasing over time for only one of the arms as grew. Further, bifurcated and regrown arms were utilized more in safe behaviors than risky ones, with more severely injured arms showing a higher frequency of use in safe behaviors. These findings contribute to the growing knowledge of arm usage in octopuses, suggesting that arm bifurcation may lead to branchial neural differentiation and potentially indicate post-traumatic associated in O. vulgaris.

Anatomical abnormalities in octopuses, whose behavior is facilitated by flexible neuron-rich arms, offer insights into life histories and the neurological implications of understudied conditions such as bifurcation. Although documentation is scarce, here we present in-situ videos of 9-armed O. vulgaris with a functional bifurcated R1 arm. Analysis using RDAs and GLMs investigated the impact of the bifurcated arm on behavior and examined changes during growth. Analysis revealed a differential usage of between the bifurcated arms in addition to an initial specialization of the bifurcated arms for actions below the body, decreasing overtime as the arms grew. Further, bifurcated and regrown arms were utilized more in safe behaviors than risky ones, with more severely injured arms showing a higher frequency of use in safe behaviors. These findings contribute to the growing knowledge of arm usage in octopuses, suggesting that arm bifurcation may lead to branchial neural differentiation and potentially indicate post-traumatic associated in O. vulgaris.

The Atlantic blue crab, Callinectes sapidus , has rapidly expanded its invasive range ubiquitously in the Mediterranean Sea, posing ecological threats to native ecosystems. In its native habitat, the crab plays a crucial role in the ecosystem, but in invaded areas, it lacks natural predators. This has led to rapid expansion, highlighting the need to monitor and understand biological interactions with the native community. This study reports, for the first time in the wild, the predation of the invasive blue crab by the common octopus, Octopus vulgaris , in the Mediterranean Sea. Three sequences (two videos and a photography series) recorded by two spearfisherman (observation 1 and 2) and a recreational SCUBA diver (observation 3) are described. This article highlights the importance of native predators in influencing the expansion or control of invasive species. Additionally, it showcases the capacity of a versatile predator (the octopus), to serve as an ally alongside the fishing strategy, suggesting a novel perspective for ecologically sustainable management, in a context of low native predators of the blue crab. The collaboration with citizen scientists proves crucial in expanding our understanding of predator–prey dynamics and ecological interactions, underlining the need for continued partnerships between researchers and society for effective invasive species management.

Achieving sustainable resource use is a priority to meet future challenges. The Gulf of Cádiz, located in the Atlantic waters of southern Europe, is home to a significant fishing fleet due to the richness and diversity of its ecosystems. Managing this area is complex due to the diversity of variables, including social, ecological, and oceanographic factors. Therefore, multidisciplinary approaches are proposed for implementing conservation strategies. One strategy for defining area-based management measures is through the use of flagship species, such as seahorses. These emblematic animals can assist in defining such measures. However, there is currently scarce information on the occurrence of seahorses in the Gulf of Cádiz. In this study, we present the first occurrence data of two species of the genus Hippocampus (H. hippocampus and H. guttulatus) in this area. The Gulf of Cádiz is not only described as the southernmost region of their distribution in continental Europe, but it is also a significant landmark for the genus Hippocampus, as one adult was captured at a depth of up to 101 m. Five management areas based on differentiated benthic habitats are proposed. We believe that our study has the potential to significantly improve conservation of seahorses and induce a positive impact on the ecosystem.

It is accepted that loliginids, like other squid, deposit their eggs in crevices on the seabed and then abandon them. In this work, we present observational evidence of egg guarding behavior in wild European squid, Loligo vulgaris. While monitoring a squid spawning crevice at night in Spain, a large mass of squid eggs was located and filmed 17 times during 42 days, until hatching. A male and a female of L. vulgaris were filmed in front of the crevice. The same male was filmed guarding the eggs on consecutive days. In the presence of the divers, male and female alternated their approaches to the crevice repeatedly touching and flushing the egg clusters. This guarding behavior differs from the reproductive habits assumed for the European squid and could represent the first evidence of egg guarding by a male in cephalopods.