Movement of three stream‐resident balitoroid loaches and a goby in a Hong Kong hillstream

Abstract

We undertook a mark–recapture study of three pool‐dwelling balitoroid loaches and a nonmigratory goby in a Hong Kong hillstream, which extended over a 35‐week period. The target species were Pseudogastromyzon myersi and Liniparhomaloptera disparis (Balitoridae), Schistura fasciolata (Nemacheilidae) and Rhinogobius duospilus (Gobiidae). Recapture rates of tagged individuals were high (58% overall), especially for the abundant R. duospilus (70% of 412 tagged) and P. myersi (57% of 762 tagged). At the end of the study, most recaptured individuals (78% of gobies, 62% of P. myersi, 42% of L. disparis and 67% of S. fasciolata) were within the pools where they had been released. Of those that had moved elsewhere, maximum displacements ranged from 46 m (R. duospilus) to 101 m (P. myersi), giving rise to a strongly leptokurtic distribution of movement distances. Mean displacements after 35 weeks ranged from only 2.9 m (R. duospilus) to 10.0 m (L. disparis). The sedentary behaviour of these species was more marked than most other small benthic fishes, although our study excluded the breeding period and wet season when high flows might have stimulated movement. Among the mobile P. myersi individuals, most travelled upstream, whereas mobile gobies tended to move downstream. Juveniles of P. myersi and R. duospilus, as well as large adult P. myersi, were especially sedentary, while mobile adult P. myersi that travelled further showed smaller growth increments. The highly sedentary habits of all four fishes suggest that they may exert persistent local top‐down control of benthic communities within pools in Hong Kong streams.

Are high densities of fishes and shrimp associated with top‐down control of tropical benthic communities? A test in three Hong Kong streams

“…Control pools were subject to temporary removal of stones, wading and electrofishing, but no macroconsumers were removed. No block nets were installed because mark–recapture studies in Hong Kong streams have demonstrated the highly sedentary nature of Hong Kong fishes and the shrimp M. hainanense (Mantel & Dudgeon, ; Ho & Dudgeon, ), suggesting that recolonisation of defaunated pools during the 4‐week study period would have been negligible (see also Martin‐Smith et al ., ).…”

Genetic legacy of tertiary climatic change: a case study of two freshwater loaches, Schistura fasciolata and Pseudogastromyzon myersi, in Hong Kong

“…S. fasciolata and P. myersi are well adapted to fast-flowing streams, but they may be swept downstream during a downpour in the rainy season. A recent markrecapture study in Hong Kong reveals a marked difference in their mobility: rheophilic behaviour is common in balitoroid loaches, and P. myersi shows a particularly strong tendency to move upstream (Ho and Dudgeon, 2015). In contrast, S. fasciola is sedentary with limited movement along the stream.…”

“…Indeed, recent population genetic studies of freshwater shrimp, Caridina cantonensis, revealed strong genetic divergence and a low level of gene flow among populations within and among drainage systems (Tsang et al, 2016). The freshwater goby, Rhinogobius duospilus, which is a sedentary stream fish (Ho and Dudgeon, 2015), showed even stronger population differentiation and the pattern of population structure follows the Late Pleistocene paleodrainage pattern (Wu et al, 2016). However, with only two ecologically different and phylogenetically distant freshwater species examined in this region, it is unclear whether the observed patterns are common in multiple freshwater taxa in Hong Kong, and whether there were general historical causes that similarly shaped the population genetic structure of local stream inhabitants.…”

“…The target species are two loaches, Schistura fasciolata and Pseudogastromyzon myersi. They are small benthic balitoroid loaches (TLo10 cm, Ho and Dudgeon, 2015) that widely coexist from middle to upper streams in Hong Kong and obligate to freshwater (Dudgeon, 1992). There are, however, subtle differences in their ecological traits: S. fasciolata is commonly found in East Asia streams on both stony and sandy substrates and mainly feeds on benthic micro-invertebrates and algae, while P. myersi is an algivorous loach endemic to the Guangdong province of mainland China that prefers streams with a stony substratum and abundant algal supply (Lee et al, 2004;Yang and Dudgeon, 2009).…”

“…There are, however, subtle differences in their ecological traits: S. fasciolata is commonly found in East Asia streams on both stony and sandy substrates and mainly feeds on benthic micro-invertebrates and algae, while P. myersi is an algivorous loach endemic to the Guangdong province of mainland China that prefers streams with a stony substratum and abundant algal supply (Lee et al, 2004;Yang and Dudgeon, 2009). A recent markrecapture study of these species in Hong Kong suggests that these species are highly sedentary, with a high recapture rate (62% of P. myersi and 67% of S. fasciolata) comparable to that of the freshwater goby R. duospilus (70%; Ho and Dudgeon, 2015). By analysing the phylogeographic patterns based on sequence variation in the mitochondrial control region (CR), the nuclear interphotoreceptor retinoid binding protein gene 2 (IRBP), and an exon-primed intron-crossing marker from ribosomal protein S13 (R13), we tested (1) if past climatic and geological events have exerted similar effects on the phylogeography of these sympatric species, and (2) if their highly sedentary nature confers a similar level of fine-scale genetic differentiation in these species.…”