Sawfishes are among the most threatened families of marine fishes and are susceptible to incidental capture in net fisheries. Since bycatch reduction devices currently used in trawl fisheries are not effective at reducing sawfish catches, new methods to minimise sawfish bycatch are needed. Ideally, these should affect sawfish behaviour and prevent contact with the fishing gear. We tested the effects of electric fields on sawfish behaviour to assess the potential of electric pulses in mitigating sawfish bycatch. Experiments were conducted in a tank where 2 electrodes were suspended in the water column, connected to a pulse generator, and placed across the swimming path of sawfish. Two largetooth sawfish Pristis pristis were tested in control conditions, in the presence of a baseline pulse, and of 5 variations of that pulse where 1 parameter (polarity, voltage, frequency, pulse shape, pulse duration) was altered at a time. Conditional inference trees were used to identify the effects of various parameters (e.g. treatment, individual) on reaction type, re action distance, twitching presence and duration, and inter-approach times. Sawfish reacted to electric fields, but reaction distances were small (typically <1.2 m), and no field tested consistently led to reactions conducive to escaping from moving nets. The following parameters induced the most response in both individuals: bipolar current, rectangular shaped, 5−10 Hz, ~1500 μs duration, and 100 V. We recommend further research focussing on moving nets, testing a V-shaped electric array preceding the net mouth by at least 5 m, and testing a setup similar to electrotrawling.

Extinctions on land are often inferred from sparse sightings over time, but this technique is ill-suited for wide-ranging species. We develop a space-for-time approach to track the spatial contraction and drivers of decline of sawfishes. These iconic and endangered shark-like rays were once found in warm, coastal waters of 90 nations and are now presumed extinct in more than half (n = 46). Using dynamic geography theory, we predict that sawfishes are gone from at least nine additional nations. Overfishing and habitat loss have reduced spatial occupancy, leading to local extinctions in 55 of the 90 nations, which equates to 58.7% of their historical distribution. Retention bans and habitat protections are urgently necessary to secure a future for sawfishes and similar species.

This report details two surveys of Green Sawfish (Pristis zijsron) at two sites in Garig Gunak Barlu National Park in the Northern Territory. Weather conditions and limited water clarity restricting usable video footage from drones at one site (Lidarnardi) during survey 2. The use of Baited Remote Underwater Videos were unsuccessful. Drones recorded Green Sawfish on 88% of survey days and 30% of transect flights. Sawfish numbers ranged from 1–8 individuals per transect and density from 3.8–30.5 per hectare (the highest density of sawfish ever reported). Sawfish ranged from 57–167 cm total length (TL), with most 60–100 cm TL, suggesting a nursery area. The surveys confirmed the presence of juvenile Green Sawfish in intertidal waters of the national park, suggesting the park waters represents critical habitat, and provides the species some refuge from major threats. However, similar inshore intertidal habitat is not well represented in northern Australian protected areas.