Killis of Spain Pt. 3 – Aphanius baeticus

By Matt Ford

The ‘fartet’, Aphanius iberus (Valenciennes, 1846), was considered the only Spanish representative of the genus for over 150 years. However, in an example of how taxonomy has been increasingly influenced by modern phylogenetic techniques in recent years, studies published around the turn of the century revealed the populations found along the country’s Atlantic coastline to be genetically different to Mediterranean ones.

This information was subsequently analysed alongside morphometric data then used to characterise these populations, resulting in the erection of a new species name for the Atlantic-coast fish. Aphanius baeticus (Doadrio, Carmen and Fernández-Delgado, 2002), commonly-referred to as ‘salinete’ in Spain, probably diverged from its Mediterranean sister when the Straits of Gibralatar opened around 5 million years ago but the two retain many similarities and are now threatened by the same anthropogenic factors.

Body patterning appears near-identical at first glance with males sharing the same basic arrangement of vertical stripes concentrated in the rear portion of the body and females irregular dark markings on a pale background. However, according to the description, the bars in males are relatively thicker in A. baeticus than A. iberus, and the dark markings in females few and relatively large in A. baeticus, numerous and relatively small in A. iberus. Having seen examples from several localities of both species these characters seem to hold true for females, less so males as some individuals of A. baeticus possess similarly thin bars to A. iberus, in some cases even more so.

There are minor morphological differences too. A. baeticus possesses 9-11 (usually 10) branched anal fin rays and 8-9 (usually 8 ) branched dorsal fin rays vs. 8-9 branched anal fin rays and 8-9 (sometimes 10) branched dorsal fin rays in A. iberus. A. baeticus also lacks the yellow pigmentation seen in the ventral and anal fins of some A. iberus populations. Body shape is perhaps the most useful identifying character because A. baeticus is the more elongate, deep-bodied fish and has a noticeably shorter, more rounded snout than A. iberus. At any rate when the species are viewed side-by-side the distinction is normally clear.

Reproductive biology is basically identical with A. baeticus exhibiting the same suite of adaptations to fluctuating environments discussed for A. iberus in the previous post. Diet is also much the same. However while the remaining populations of A. iberus tend to exist in brackish lagoons, A. baeticus mostly inhabits small, first-order streams. Some of these are temporal and subject to annual drying events with the fish surviving in remnant pools for several months each year, while water chemistry varies from pure freshwater to hypersaline depending on locality.

Distribution comprises the lower Río Guadalquivir basin plus a disjunct series of localities along Spain’s Atlantic coastline as far as the town of Tarifa on the Straits of Gibraltar. There are also unconfirmed reports of a population existing on Gibraltar itself but little information is available. This species has penetrated the aquarium hobby to an even lesser extent than A. iberus, presumably as a result of relatively reduced international tourism across its range plus its protected status.

Some populations have already been destroyed and of the nine remaining only a couple are pristine, the main problem being introduction of the alien competitors Fundulus heteroclitus and Gambusia holbrooki; at localities where it occurs alongside one of these A. baeticus shows marked reductions in population density. It’s classified as ‘Endangered’ by the IUCN and included in the Spanish National Catalogue of Endangered Species.

Unfortunately in most cases habitat management is equally intensive as for the majority of extant A. iberus populations i.e. non-existent. For example, the Río de la Vega in Andalucía is one of the few places where A. baeticus still comprises part of a natural fish species assemblage (though the invasive red swamp crayfish, Procambarus clarkii (Girard, 1852), is present). It’s a seasonal stream running alongside the aforementioned town of Tarifa and dries to a series of small pools on a more-or-less annual basis. The killis are restricted to a short freshwater section of several hundred metres which they share with the endangered loach Cobitis paludica (de Buen, 1930), also endemic to Spain, plus a selection of marine fishes such as Atherina and Liza spp., smaller specimens of which often become trapped in the pools when the stream dries.

Despite the relatively intact state of the habitat access isn’t restricted in any way and there’s no signage to suggest that it houses endangered or protected species. When the bed is dry horses are allowed to drink from/defecate/walk into the pools and it’s used as a thoroughfare for locals with motorbikes since it provides a short-cut into town. A farmer has been allowed to fence the stream off which is not only illegal but prevents passage; therefore we still don’t know how far upstream the fish can be found. The section with the highest density of Aphanius is now bordered on one side by a small industrial estate and lower down threatens to be encroached by the town itself. The IUCN note that this species may be extinct within the next decade and sadly this appears to be born out by the facts gleaned from this and other localities unless something drastic happens.

Next time we’ll look at Valencia hispanica (Valenciennes, 1846); arguably the most beautiful representative of Spain’s endemic fish fauna and of even more precarious conservation status than the two Aphanius species, after which I pledge to contribute a little more happiness to this blog!