Microphis leiaspis, Bleeker, 1854

Ebner, Brendan C., Maeda, Ken, Donaldson, JamesA., Harasti, David, Lord, Clara, Haÿ, Vincent, Heffernan, Jason, Starrs, Danswell, Thuesen, Paul, Beatty, Stephen, Boseto, David, Copeland, Lekima K. F., Rashni, Bindiya, Hevalao, Robson S. & Keith, Philippe, 2023, Pebbled places preferred by people and pipefish in a World Heritage protected area, Cybium 47 (4), pp. 401-416 : 404-405

Microphis leiaspis was only observed occupying shallow water, with 52 cm being the deepest an individual was recorded occupying. In Emmagen Creek where most of our samples were encountered (n = 21), individuals selected for moderate flowing (0.2-0.5 sms –1), moderately shallow water (0.25-0.50 cm depth), on pebble-cobble benthos ( Fig. 2 ). In Oliver Creek, only five individuals were observed and quantified for microhabitat use. These small sample sizes precluded clear indications of selectivity but reinforced that M. leiaspis occupies pebble-cobble habitat receiving intermediate benthic flows ( Fig. 2A, C ). Individuals in Oliver Creek inhabited very shallow water ( Fig. 2B ). Of the gobioids studied, this microhabit niche most aligns with Schismatogobius hoesei , but the latter prefers a greater proportion of sand in which to bury (cf. Donaldson et al., 2013).

Occasionally, the larger streams in Cape Tribulation exhibit isolated patches of the macrophyte Blyxa , typically in partially sandy areas. However, a general absence of aquatic macrophytes is a notable feature of the short-steep-coastal-streams within the AWT. Nevertheless, M. leiaspis has not been observed associating with Blyxa .

Additional behavioural and habitat use observations of adult M. leiaspis come from our collective experiences over a much wider temporal and spatial window in several streams in Australia (e.g., BE & JD snorkelling in SSCS between 2009-2022) (JH in the Mossman River 2019-2022), in Okinawa, Japan (KM 1996-2022), the Solomon Islands (RH 2015-2022) and opportunistically across the Pacific Islands (DB, CL, PK, KM, JD, BE). These observations confirm that the longitudinal distribution of adult M. leiaspis is the lower-middle course of perennial streams. They also confirm that M. leiaspis is rarely seen where sand is available, nor where bedrock and boulders are the dominant features of the benthos. Pebbles, and to a lesser degree cobbles, are the dominant feature of their core range. Occasionally individuals are seen moving into or out from boulder fields and cascades at the head of pools (e.g., in Noah Creek, Cape Tribulation, Australia, BE). The behaviour and habitat associations of M. leiaspis may therefore be more boulder associated than is acknowledged here, and in fact, there may be a quasi-subterranean component to their existence in a subset of streams (i.e,. complex boulder stream beds where the surface water passes below the upper boulder surface). In larger rivers of the Solomon Islands, the species does occur on the floodplain sills but only where exposed cobble and pebble habitat exist as a function of regular fluctuations in discharge rather than on silted or muddy floodplains (RH, pers. obs.).

Figures

Figure 2. – Selectivity (± 95% confidence interval (CI)) of Microphis leiaspis for categories of A: Flow velocity; B: Depth; C: Substratum type and D: Flow type, used v. availability across two streams. Selectivity values greater than or equal to 1.0, indicated by the red dashed line (including 95% CI) indicate positive selection by M. leiaspis toward a given category, while values less than 1.0 (including 95% CI) indicate negative selection.