heliastes21's Journal

In October I was fortune enough to go on holiday to Malta. Whilst being somewhat disappointed at the sheer lack of diversity in the bird species we observed, I was taken by the many ‘Filfola lizards’ that we spotted throughout Valletta and elsewhere in Malta and Gozo. The filfola lizard or Maltese wall lizard (Podarcis filfolensis) is a species in the family Lacertidae. In the Maltese Islands, there are four subspecies , all of which are endemic there.

Podarcis filfolensis ssp. Maltensis is the subspecies found on the three main islands: Malta, Gozo and Comino. It is normally greenish and sometimes speckled. Podarcis filfolensis ssp. Filfolensis is endemic to the tiny islet of Filfla just off the coast of Malta; it is the largest of the four subspecies and is blackish with bluish spots. Podarcis filfolensis ssp. Generalensis is endemic to Fungus Rock (west coast of Gozo); it has a reddish belly and blue-like flanks. Podarcis filfolensis ssp. Kieselbachi is endemic to Selmunett, otherwise known as St.Paul's Islands. Its colours vary greatly e.g. brown, grey, etc. with an orange belly and small black spots. The population became extinct in 2005. Other sub-species are thought to inhabit the nearby Pelagian Islands of Italy.

Between 1997 and 2000 I carried out PhD research on the Mediterranean damselfish Chromis chromis in Corsica (France), yet it is only recently that I have included observations of this species in iNaturalist. In 2018 I published a paper explaining why Chromis chromis are one of the most important species in the Mediterranean (see doi:10.1111/jfb.13551).

The damselfish Chromis chromis is typically the most abundant fish species in the rocky littoral environment of the Mediterranean Sea, where it feeds in huge shoals on incoming zooplankton and rests near the seabed each night. Research has shown that large populations of C. chromis play a fundamental role by transferring carbon, nitrogen and phosphorus directly from the pelagic system to the littoral in the form of solid and liquid wastes and therefore that this species acts as a vital conduit for nutrients. In addition, C. chromis represents a major prey item for predatory fish and seabirds, it has been shown to exert significant predation pressure on coastal zooplankton populations, but it is also a major consumer of fish eggs and hence may have a strong influence on the dynamics of other fish species. Chromis chromis is of only minor importance to commercial fisheries (it is usually discarded), but trends in population abundance of this species can be indicative of levels of fishing pressure on other commercial species. It has been demonstrated that where predator numbers are able to recover from intensive fishing (e.g.in marine protected areas), this is often mirrored by lower densities of C. chromis. Several papers have championed C. chromis as a possible indicator species for human disturbance. As well as being directly and indirectly affected by fishing, the species is also sensitive to a number of other anthropogenic pressures, most notably poor water quality and noise pollution.