As the survey has progressed northwards, from tropical to temperate waters, the fauna have changed. From the amazing tropical fauna, full of colours, to more discrete specimens that becomes more similar to the European fauna. Each time the trawl arrives on deck we are excited to see what’s in. It is far too early to sum up the main results from the survey but we have notices some unusual occurrences. Below we will share some of these new and exciting findings with you. (see more pictures at the bottom of the page)
Last week we did find a fish which we believe have not been reported before. The specimen is belonging to fishes called rovers, Emmelichthyidae, in the genus Emmelichthys. This family, consisting of only three genera and about 15 species, is found in tropical and warm temperate waters and they are feeding on plankton. Adults are usually found near the bottom from 100-400 m depth. The individual we caught was not described in any of the literature we have available onboard. After some e-mailing with specialist on land, we realized that this can be a new species. What a joy. A tissue sample has been conserved in ethanol for genetic analysis and the specimen itself was conserved properly in order to send it to a taxonomist when the cruise is over. Two days later we caught five more of this fish. Unbelieveable!
Another day we caught a fish that lives in the cavity of a sea cucumber. One fish species, Carapus acus, in Eastern Atlantic is fairly well known for this behaviour and we recorded it on the survey last year to São Tomé. The specimen we caught this time was smaller and looked different from the previous one. May be it is an early stage or another species?? This specimen will also be sent to a specialist for further examination.
Sometimes it can be really difficult to differentiate between species. We have to count gill rakers, spines etc., and big discussions between the expert’s onboard starts. Internet and various other literatures are checked and usually everybody agrees and they have all learned something new that day. Since it is so small details that distinguish one species from another, it is quite common that the locals identify the most common species for the area, without considering the possibility that it can be a close relative. We had one on those discussions yesterday about three types of hake (Merluccius senegalensis, Merluccius polli and Merluccius merluccius).
Other findings are related to additional groups that are not very well known, for instance the Hydroids. We have collected colonies of the genus Diphasia and Nemertesia that could not be assigned to any of the species presently known. This leads us to think that they may belong to new species.
Other more common species still surprise us with their amazing colours and shapes, as exemplified by the lentil bobtail Rondeletiola minor, the pink glass shrimp Pasiphaea multidentata, the Heterocarpus ensifer or the hermit crabs Dardanus arrosor.
Preliminary observations also reveal new information on the distribution of many species. For example, the distribution of horse mackerel T. Trachurus was found on the shelf south of Dakar. This is quite unusual at this time of the year, and the frequencies of occurrence in the trawl catches were higher than any previously recorded. This is also the case of two species of octopus the Musky octopus Eledone moschata and the spider octopus Octopus salutti, whose southern limit previously was believed to be in the Gulf of Cadiz, but which we now have found along the coast of Morocco.
Lack of occurrence
The abundance of sardines is extremely low. We did find some occurrence off the coast of Mauretania, but further north, in the previously main area for sardines, we did not catch anything, nor did we see any schools on the eco sounder. Also the number of octopus in the catches have been much less than expected.
The transects north of Cap Juby have seen large changes in both the abundance and species composition of seabirds in comparison with lower latitudes, for example pomarine skua Stercorarius pomarinus has been replaced by great skua Catharacta skua as the main food robber at trawls. Perhaps coinciding with the low sardine numbers noted above, the abundance of Northern Gannets Morus bassanus is much less than further south, although this is still the dominant species and large numbers have attended trawl discards. (Photo).
Many hundreds of Great Shearwaters Puffinus griseus has been a surprise. Breeding individuals are on nests on Tristan da Cunha near the Antarctic now, so this seems to be a newly discovered wintering location for non-breeding birds, or very late migration. Mediterranean gull's Larus melanocephalus wintering behaviour is not known, so many observations, all of birds in their first year, over the continental shelf, including both day and night foraging at trawls, are a first. The globally “Critical” Balearic shearwater Puffinus mauretanicus is the most threatened seabird of the CCLME. Though more characteristic of the Mediterranean and coastal SW Europe, our observations in recent days, at the edge of its wintering range, will be of interest to analyses.