First recording of Portuguese dogfish shark in Maltese waters
Photo by Jesmond Dalli, shows a good number of rough sharks for sale at the fisheries landing site as such, however these are indeed gulper sharks (Centrophorus granulosus).
A shark species - the Portuguese dogfish (Centroscymnus coelolepis) - has been recorded in Maltese waters for the first time.
The Portuguese dogfish is a deep water dwelling shark, found at depths of 200-3,500 metres. Although it has a maximum length of 120cm, it is usually found at 90cm.
The recording of the shark forms part of a detailed scientific study and field work that focused exclusively on sharks and rays.
The study was conducted over the past two years as a Master's level research project within the Conservation Biology Research Group of the University of Malta's Biology Department.
Jesmond Dalli, working under the supervision of conservation biologist Adriana Vella, made the study of this group by using local scuba and fisheries surveys.
The work considered the elasmobranches (shark and ray species) from both local and biological perspectives in order to provide a first detailed recognition of the way each species was being affected by local human pressures.
The aim was to go beyond the normal records, such as the listings of species encountered by fishermen at fish landing sites and to look at the life stages of species caught with different fishing gear.
Apart from the fishing impact, the abundance of different species around the Maltese coasts was also studied through scuba diving surveys undertaken year round.
As a basis to this detailed field work, an extensive literature survey and compilation of all data gathered on this group was reviewed and critically assessed.
Fisheries statistics dating back to 1948 and held by the National Statistics Office were studied.
But most of these records were limited since the different species were not specified but were grouped. This limited their validity and pointed to an important management problem - a lack of detailed species record keeping. This could be due to the fact that categories used by the fisheries department to record the majority of the elasmobranches landings considered numerous species as one. This did not make sense biologically as the different species would have contrasting life histories and different conservation needs.
Such categorisation provided a great problem due to the fact that some species were more sensitive to exploitation than others, possibly overlooking the effects of exploitation on the more sensitive species.
Another problem was the indiscriminate exploitation of these species, where in some cases even new born and gravid individuals were landed. Such exploitation was highly unsustainable due to the fact that only small numbers would be left to grow and contribute to future generations.
The study compiled data on the biological parameters for each species to provide further understanding as to the extent to which local fishing practices and elasmobranches needed sustainable and conservation management.
A coastal scuba study around the Maltese coastal waters provided information on the distribution and the habitats of the species found in Maltese coastal waters.
The results obtained from this field scuba survey, held for the first time to purposely investigate coastal elasmobranches, revealed poor species diversity and an abundance of this group around the Maltese islands.
So while numerous species were caught offshore very few species were found closer to coast and most coastal elasmobranches spotted occasionally close to coast rarely stayed for long.
The majority of the elasmobranches found coastally belonged to the rays family and were found on sandy bottoms. This showed that sandy seabeds were important habitats that needed to be safeguarded and should not be considered as a dead substratum.
Important hotspots of abundance at particular times of the year were discovered pointing towards the need for coastal and offshore marine conservation areas that would allow for local elasmobranches to be protected effectively.
Management plans for the protection of these species were of utmost importance for their protection.
These included the fine-tuning of fishing techniques to reduce the species caught in order to ensure sustainability.
Other measures such as area and season closures, together with the addition of more species to the list of protected elasmobranches should also be taken into consideration.
The education of fishermen and the public was also very important.
This research was presented as one of the contributions at the biodiversity conference organised by the Malta National BioPlatform last month.
Assistance from several officials at the fisheries landing section, fishermen, members of scuba diving schools was obtained during this study together with that from the members of the Biological Conservation Research Foundation who provided assistance as part of their marine biodiversity surveys.