Investigating the use of artisanal style shelter fishing pots for Octopus vulgaris as artificial dens to increase habitat availability and the abundance of Octopus vulgaris in Gibraltar
Eleanor Clay
Abstract
Octopus vulgaris are a species that inhabit the coastal waters of Gibraltar and are a popular food source throughout Gibraltar, Europe, and the rest of the world. Fishing for Octopus vulgaris in Gibraltar is common and may cause a pressure on the abundance of Octopus vulgaris in Gibraltar. Widespread habitat homogeneity and degradation from anthropogenic activities can limited shelter material for Octopus vulgaris which can also limit the abundance of Octopus vulgaris. Artisanal octopus fishing methods employ a shelter technique where an amphora style shelter pot is laid on the seafloor to catch Octopus vulgaris through exploiting their need for shelter. The current research aims to use artisanal style shelter fishing pots as artificial dens for Octopus vulgaris to increase habitat availability and abundance of Octopus vulgaris in Gibraltar. Occupancy of the artificial dens in Camp Bay, Gibraltar 27 days post deployment was 35 % with an increase in occupancy of 75 % from 19 days post deployment (20 %) to 27 days post deployment (35 %) and citizen science observations post research surveys indicate continued increases in occupancy. This is the first research of this kind to introduce a low-cost Nature-Based Solution to increasing habitat availability and consequently potential to increase the abundance of Octopus vulgaris in Gibraltar through repurposing artisanal fishing pots as a conservation tool. Recommendations for continuation of this Nature-Based Solution include deploying these artificial dens on a wider scale in Gibraltar within ‘no take’ marine conservation zones and education of the public and local fisherman to increase success in conserving Octopus vulgaris in Gibraltar.
Shooting the Stars’ An Ecological Assessment of the Distribution and Health Status of Astroides calycularis in British Gibraltar Territorial Waters
Sid Dewfall
Abstract
Astroides calycularis is an important bioindicator species for fluctuations in environmental stability. The orange stony coral is sensitive to changes in oxygenation and temperature, playing an important role as an indicator for climate change and disturbances within the local marine environment. As an ecosystem engineer, A. calycularis enhances coralligenous assemblages, increasing habitat complexity and promoting biodiversity. This study analyses the distribution and health status of Astroides calycularis within Gibraltar. To investigate this, a simple and cost-effective methodology was devised based on a systemic and critical literature review of monitoring protocols and health assessments on soft and stony corals. The methodology evaluated the use of photo-quadrats on two dive sites; Seven Sisters, a natural rocky reef, and Batty’s Barge, an artificial reef created in 1990. Through collection of photo-quadrat replicates, the use of citizen divers allowed for the monitoring protocol and methodology to be tested in situ to gather feedback for the publication of a PADI Distinctive Speciality. Citizen science was used to provide evidence on the proposed course and resulted in a larger dataset for the study. Our analysis shows that A. calycularis colonies are healthy and widely distributed within Gibraltar’s waters, with an average colony size of 29.62 cm 2 and a percentage of colony alive of 90.31 %. Colonies were spotted across a number of wrecks and rocky reefs throughout the sampling period, and the distributions were mapped. The results indicated that A. calycularis is more abundant and healthier at Seven Sisters than Batty’s Barge. From a total of 243 colonies assessed, 55 % of them were located at Seven Sisters. On average, colonies were seen to be 32 % greater and 11 % healthier at the Seven Sisters study site. It was hypothesised that Seven Sisters produced better results due to stricter regulations for fishing, diving, and boating around the site, and because of the sites hydrodynamic regime. Batty’s Barge is a more exposed site to anthropogenic pressures such as human disturbance. Research shows that A. calycularis colonies have previously been affected by SCUBA divers and snorkellers across the Mediterranean, with colonies being damaged deliberately or inadvertently by diver’s physical touch or contact from dive equipment such as regulator hoses and fins. Diver education workshops and better training must be undertaken to empower divers with the knowledge of the marine environment, it’s sensitivity, and how to conduct themselves better underwater. Through the research found within this study, a robust baseline dataset on the distribution and health status of Astroides calycularis within Gibraltar has been generated, and a standardised monitoring protocol with feedback from divers will allow for future workshops to take place, educating recreational and citizen divers, and processing a new PADI Distinctive Speciality on monitoring benthic communities.
Rays of hope: The first study conducted on the species richness and conservation of batoid populations in the British Gibraltar Territorial Waters (BGTW)
Peyton Dryer
Abstract
Batoidea is a superorder of cartilaginous fish made up of stingrays, electric rays, skates, guitarfish, and sawfish which inhabit marine environments all over the globe. Species range vastly in their habitat preferences and behavioural patterns. For example, they are categorised as either pelagic or demersal fish and can be found in a variety of ecosystems including coastal, deep water, estuarine, freshwater, saltwater, cold-water, temperate, tropical, and subtropical. As rays are predatory fish they play a key role in the food web, however, they face many anthropogenic threats that have caused global population declines over the past four decades. The purpose of this study is to provide supporting evidence of what batoid species are present in the British Gibraltar Territorial Waters (BGTW), to deliver a systematic literature review about ray conservation in the Mediterranean, and to identify knowledge gaps that will establish pathways for future research. As the first scientific study in Gibraltar on rays and skates, a baseline of species richness was constructed using multiple methods. A field study took place from May to July of 2022 utilising monitoring techniques such as Baited Underwater Videos (BRUVs), diver surveys, and citizen science to collect baseline data. Based on the results of this research, batoid species richness consists of five primary species: eagle rays (Myliobatis aquila), undulate rays (Raja undulata), marbled torpedo rays (Torpedo marmorata), common stingrays (Dasyatis pastinaca), and blonde rays (Raja brachyura). Another conclusion of this experiment is that diver surveys and citizen science are more effective and efficient methods of data collection for a highly mobile species than using BRUVs. Due to the close proximity to the migratory highway it is likely there are more species not included in the results as data collection was restrained by time and likely did not include the less common species that are present in the BGTW. More research for this region concerning the abundance, conservation, and management of elasmobranchs is necessary for the preservation of this marine ecosystem.
