A new and improved electric fish finder with resources for printed circuit board fabrication

Abstract

We describe the circuit design, construction, and operation of a field-portable electric fish finder (an AC-coupled wide-band differential bio-amplifier with loudspeaker output). This device permits detection and monitoring of the electric organ discharges generated by neotropical gymnotiform fishes (as well as the mormyroid fishes of tropical Africa). Our design is modified from earlier versions to optimize detection performance and stability over a wider range of ambient water conductivity, including under conditions of extremely low conductivity (< ca. 10 μScm-1). Our new electric fish finder design also incorporates complete waterproofing and longer battery autonomy. We provide Gerber and Eagle files made with the electronic design automation software ‘Autodesk Eagle’ to allow researchers to order printed circuit boards directly from commercial manufacturers.

Geomorphological habitat type drives variation in temporal species turnover but not temporal nestedness in Amazonian fish assemblages

“…To maximize sampled species diversity in river and floodplain sites, we sampled with gill nets deployed ca 30 m from the shoreline in batteries of four (25 × 3 m, 15, 30, 45, 60 mm mesh) from 06:00 to 09:00 and from 18:00 to 21:00. In the much smaller habitat volumes of terra firme and shield streams, we used three gear types, each with a timed effort of 2 h/sampling event during daylight hours: a 1.5 × 6 m seine net (5 mm mesh) in deeper pools; a 2.0 × 1.1 m bag‐seine (2 mm mesh) in riffles and margins; a dipnet (with 3 mm mesh and 30 cm bag depth), used with the aid of an electric fish finder (Haag et al 2019), in leaf litter and marginal root mats; the dipnet‐electric fish finder combination sampled gymnotiform electric fish and other nocturnally active fish hiding in the substrate. For each stream, all gear types were used along a 100 m stretch in a downstream‐upstream direction with the ends of the section blocked with net panels to minimize escape.…”

Reproductive effort and terminal investment in a multispecies assemblage of Amazon electric fish

“…All sampling was conducted at night, from the end of astronomical twilight until as late as 02:00, during the period of peak electric fish activity. Abundances were quantified by timed capture‐per‐unit effort (CPUE), as individuals/h, using a custom‐made electric fish finder to locate Brachyhypopomus (Haag et al, 2019) and a dipnet to then capture them (Regular Hex Trapnet with 3 mm mesh and 30.5 cm bag depth; Duraframe Dipnet, Viola, Wisconsin, USA). The use of electric fish finders allowed close to 100% capture efficiency for all individuals (excepting larval and small post‐larval stages); see Waddell et al (2019) for further sampling details.…”