Who cares about the dragonets?

Diving is so calming, everything slows down and you are acutely aware of your breathing rhythms, it’s like a meditation. In the short time (too short) spent on a dive you could spot anything from 10-100 different species depending on the site, your knowledge and the patience of your dive buddy. I appreciated the beauty and elegance of it all without thinking of the functional roles each organism plays in the ecosystem.

When it comes to conservation, often scientists will try to assign a monetary value to things in order to ensure funding for studies and protection. For example, the identification of cold-water coral habitats as essential breeding ground for the Norwegian Redfish, which is of commercial importance. There is little profit to made from Dragonets which is reflected in the lack of target specific surveys. Dr Pauline King noted an absence in C. reticulatus during her sampling in Galway bay (King et al,1978). A paper written by Chang,1951 did find specimens of C. reticulatus while sampling off Plymouth for C. lyra and added it as a North Sea fish. At that time an examination of zoological museum specimens at Bergan revealed two Reticulated dragonets which had been misidentified as the Spotted dragonet (C. maculatus, Rafinsque,1810). A review of the world’s genera by Fricke, 1981, Nekado, 1982 has led to dead specimens at least being clearly distinguishable by number of fin rays and pre-opercular spines, 1st dorsal fin and pattern differences on 2nd dorsal fin (Froiland,1976).

Close-up of 2nd dorsal fin C. lyra. WoRMS,2019.
Reticulated 2nd dorsal pattern. Hans Hillewaerte,2007.

 

 

 

 

 

 

So, the Spotted confused with the Reticulated, and the Reticulated confused with the Common. Last week we were talking about habitat preference, many of the photographs of the Reticulated do appear to be on coarse substrate noted by Seasearch members also. Fricke, 2017 sampled the Mediterranean in search of C. reticulatus and noted a preference to coarse sand bottom with large shell fragments, it was believed that the grain size was similar in size to the spots on the back and sides. During this sampling a clear depth boundary was noted between the spotted and the Reticulated with the Spotted found in deeper water. Given that the Common and the Reticulated share the same food preferences (small crustaceans, gastropods, polychaete worms & small starfish) (McDermott et al,1995) it would make sense for them to have distinguished foraging grounds also to avoid competition.

Chang,1951 found C. reticulatus rare in offshore waters where as Boer,1971 found their numbers increased further away from the Dutch coast, these varied depth findings could simply be down to substrate type at different sampling locations. Then they could easily be found both at the same site but on different substrate patches. Their behaviour could also be different in different locations, breeding time is different in the North Sea versus the Mediterranean for example, and dominant prey items vary with location. A paper was published by Burgeot et al, 1993 identifying Callionymus lyra as a target species to assess pollution in the Marine environment using biomarkers, however despite its abundance its biology was not well studied, and this is an important condition. Hopefully future comprehensive studies can be performed here to characterize our Dragonets.

References

  • Boer, P.,1971. “The occurrence of Callionymus reticulatus in the Southern North Sea” ICES journal of Marine Science (33(3) pp506-509). Available at: https://doi.org/10.1093/icesjms/33.3.506 (accessed 08 April 2020)
  • Chang, H-W., 1951. “Age and growth of Callionymus lyra”. Journal of Marine Biology Association. Pp281-295. Available at: DOI: 10.3750/AIEP/02098 (accessed 22 March 2020)
  • Fricke, R. & Ordines, F. “First record of the Reticulated Dragonet Callionymus reticulatus from the Balereac Islands, Western Mediterranean”. Acta Ichthyol. Piscat (47(2) pp163-171). Available at: https:/DOI: 10.3750/AIEP/02098 (accessed 22 March 2020)
  • Froiland, O & Greve, L., 1976. “Callionymus reticulatus (Pisces, Callionymidae) from Western Norway”. Sarsia (62(1) pp1-4) Available at: https://doi.org/10.1080/00364827.1976.10411308 (accessed 02 April 2020)
  • King, P.A., Fives, J. M. & McGrath, D. “Reproduction growth and feeding of the dragonet, Callionymus lyra (Teleostei: Callionomidae), in Galway Bay, Ireland” (1994). Journal of the Marine Biological association of the United Kingdom, (volume 74, 3, pp 513-526). Available at: https://doi.org/10.1017/S0025315400047639 (accessed 17 February, 2020).
  • McDermott, S. & Fives, JM. “The diet of an assemblage of small demersal fish in the western Irish Sea”. Biology and Environment: Proceeding of the Royal Irish Academy, 1995. (95B (3) pp195-201). Available at: https://www.jstor.org/stable/20504515 (accessed 10 April 2020)
  • Wheeler, A.,1961. “Callionymus reticulatus as a North Sea fish” Annals and magazine of Natural History (4(48) pp753-754) Available at: https://doi.org/10.1080/00222936108651203 (accessed 20 March 2020)
  • Wheeler, A. (1969). The Fishes of the British Isles and North-West Europe. Michigan state University Press, East Lansing, 1969.

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