Do fish locks have potential in tropical rivers?

Abstract

This study evaluated attraction and passage of native fish through an automated fish lock on the tropical Fitzroy River in north-eastern Australia. In 69 samples (24 h each) taken at the exit and entrance of the fish lock, 17 fish species and 13 402 individuals were collected, at a maximum rate of 3317 fish per day. During low river flows, the fish lock transferred a broad size range of fish (35-710 mm long), though migratory biomass was small. Removal of a vertical fish-crowding device did not affect the passage rate. Netting studies and observations of fish migrating below the weir suggested that the entrance was poorly located during high flows and another fishway near the spillway would enhance fish passage. The fish lock was inoperative for 48% of the time, due to mechanical and software failure, and a narrow operational range unsuited to the variable hydrology. Nevertheless, these design issues are site specific and reflect that fish lock technology is in its infancy in Australia. The operational reliability of the fish lock is now greatly improved but further work is needed to optimize the automatic cycling. To accommodate the inherently variable hydrology of lowland tropical/sub-tropical rivers into fishway design, we highlight important research needs for fishways and migratory fish communities. Fish locks are often considered a less favourable fish passage option but with the operational reliability issues partially resolved, they appear to have considerable potential for tropical river systems with low minimum flows and low biomass; with further research and design, they may have wider application.

Effectiveness monitoring of fish passage facilities: historical trends, geographic patterns and future directions

“…2007b; Baumgartner and Harris 2007; Mallen‐Cooper and Brand 2007; Oldani et al. 2007; Stuart et al. 2007, 2008).…”

Movement of three non‐salmonid fish species through a low‐gradient vertical‐slot fishway

“…Despite problems of unreliable operation in fishlocks, there is continued interest in their use to pass migrating fish communities, in part because of their capacity to serve small species and relative cost effectiveness (Stuart and Berghuis, 1997; Baumgartner and Harris, 2007; Stuart et al , 2007). Models of species' movement patterns could be used to refine fishlock operating cycles and to match high‐demand times, when migrating fish are more likely to enter the fishlock.…”

“…Avoiding delayed passage may be important for reducing physiological stress, limiting opportunities for predation mortality, or avoiding loss of reproductive condition (Clay, 1995). When there is a need for concurrent passage at a site of small‐bodied fish alongside stronger swimmers, potential alternative solutions include dual (‘father and son’) fishways or fishlocks (Stuart and Berghuis, 1997; Stuart et al , 2007). These implications of cost or delays to passage through reducing bed slope in fishways, plus the scant knowledge about the limits of tolerance of small fish to turbulence, indicate an important need for further research to improve the efficiency of fish‐passage programs.…”

Can a low-gradient vertical-slot fishway provide passage for a lowland river fish community?

“…1-m variation). However, the attraction efficiency and reliability of fish locks has often been problematic (Stuart et al 2007). There is also potential to use the boat navigation lock to pass some small and large fish, but this option requires further exploration.…”