One of the main aims of the Saving Sandfish project was to find juvenile sandfish in the lower Biedouw River, catch approx. 500 or more of them and move them to the higher reaches where a healthy indigenous fish population thrives in resilient pools without alien predators (spotted bass and bluegills). Although spawning areas were frequented by scientists, spawning adult sandfish were simply not seen on the lower Biedouw this year; it was a long shot, but Dr. Jeremy Shelton and Dr. Otto Whitehead didn’t give up and with the help of several other volunteers and Freshwater Research Centre (FRC) staff they eventually found schools of juvenile sandfish in the middle to lower reaches of the Biedouw Valley. This, although no actively spawning fish were ever seen, was a clear sign that spawning happened and eggs hatched successfully.
Interested stakeholders were e-mailed and the fish rescue was scheduled on short notice a week after the FRC team had found the juveniles; but on arrival the next week they were gone…The small group of scientists and ecologists that had pitched for the rescue split up in groups and started the search all over again. After about two hours of searching two groups returned with good news, schools of juvenile sandfish were found downstream and the most fish had dropped a few kilometers downriver, closer to the Biedouw/Doring River confluence.
A total number of 610 juvenile sandfish were successfully caught and transported to the bass-free zone upstream over two days of hard, sweaty labour. Bluegills that had been trapped in fyke nets were dissected and what amazed everyone was that even the smaller bluegills, measuring around 13 cm total length, had 5 cm sandfish in their stomachs. These little sunfish may seem small, but they are ferocious little predators clearly with a big appetite.
The high numbers of bluegills in the Doring River and many of its tributaries would also explain, to some extent, the lack of recruitment of sandfish over the past 20 years, besides obviously bass predating on juveniles and even larger, young sandfish, as well as dam walls, water abstraction and the drought that all likely contributed to the decline in sandfish numbers.
Up until now, with minor stumbling blocks, Saving The Sandfish has been a major success in terms of its short term goals. The project will repeat these steps next year and also strive to achieve greater things, like establishing a big sandfish sanctuary on the higher reaches of the Biedouw in the upcoming years. Here is Dr. Jeremy Shelton’s summary of the fish rescue activities and general project update:
“Saving Sandfish: Project update 18 November 2019
I am very pleased to be able to report that we completed a successful sandfish rescue on the 5th and 6th November, and would like to send a HUGE THANK YOU to everyone who contributed (including those who couldn’t make it into the field that week). It wasn’t all plain sailing though, with unpredictable shifts in water levels and fish distributions in the lower river over the last few weeks. Here are a few of the highlights, with a more in-depth progress report to follow early in the new year. Newsletters to communicate the main findings to other stakeholders in the valley also in the pipeline.
Monitoring: gorge section
- Twelve fyke sites were established in the gorge and baseline data on fish size distributions and abundance were collected.
- These data will serve as a baseline and allow us to track survival of the relocated sandfish using repeatable fyke net surveys moving forward.
- The plan is to resurvey the same sites again next year in March 2020 and November 2020.
Monitoring: lower Biedouw River
- Fyke nets and visual surveys were used to estimate fish distributions in the lower Biedouw River
- Visual surveys showed that young sandfish were widespread in the lower 10 km of the Biedouw River during the last week of October (29th-31st October), with few bluegill and bass seen in most pools. Visual surveys were highly effective during this week because water abstraction upstream resulted in low, clear, isolated pools in the lower 10 km of river.
- However, the following week (4-8 Nov) was a different story, with the young fish apparently having moved downstream rapidly.
- High numbers of fish recorded only in the two of the downstream-most pools on the Biedouw.
- In both instances, bass and bluegill were present (confirmed by five fyke nets set in these pools).
- It is suspected that the downstream shift towards the Doring River was triggered by a pulse in flow following good rain on 25-27 October.
- Given the large numbers of bluegill in pools with young sandfish, there was concern that they may be feeding heavily on the sandfish.
- This suspicion was confirmed when Leonard looked at 15 bluegill stomachs and found young sandfish in five of these.
- Of course, these may have been consumed in the fykes where the fish were in the net together, but four of the sandfish were well-digested, suggesting they may have been consumed the previous day.
- Bluegill as small as 13.1 cm are capable of consuming 5 cm sandfish.
- In total, 610 young sandfish (approximately 5 cm in length) were collected from the downstream-most pools on the Biedouw River on 5th and 6th November and relocated successfully to several different pools in the bass-free section of the gorge.
- The fish were collected using seine nets and transported in buckets with cool, well-oxygenated water up to the gorge section on Bushmanskloof.
- The fish were slowly acclimated to the water in the gorge and released into four pools spread out through the native fish zone, including a pool near the native fish upper limit, and the large pool below the second waterfall a ways downstream.
We are excited to be working with two land owners (Enjo and Bushmanskloof) to create sandfish nurseries in farm dams by removing non-native fish and adding rocky substrates for sandfish food and shelter.
Project media: film
- Those in the field for the rescue would have witnessed Otto Whitehead in action, flying drones, capturing 360 video and generally documenting the conservation story.
- One of the highlights was an interview with Sara who has been living in near the Biedouw-Doring confluence for the last 60 years, and has a wealth of memories and insights about the sandfish in their former glory
- He has since been hard at work editing the footage and I’m really excited for everyone to see some of the outputs soon.
- We are working on three different kinds of film-related outputs for this project, each targeting a slightly different audience:
- A series of vlogs documenting the different stages of the project (target audience: partner organisations, land-owners, community, general public)
- A medium-length documentary film (target audience: everyone)
- A 360 video experience (target audience: Biedouw valley)
- December 2019:
- There is a Tankwa survey planned with EWT for 3-8 December to determine the importance of that system for sandfish
- February 2020:
- Project meeting at the FRC
- Progress report to MBZ
- March 2020:
- If all goes to plan and we get the go-ahead, preparing of Enjo Dam for sandfish stocking will take place in March.
- Rocky patches will also be installed around the perimeter.
- Follow-up fish surveys will also be undertaken in the gorge and remaining pools in the lower river.
- August 2020: Document the sandfish spawning migration by collecting ecological data (funding/student-dependent), and through film and photography.
- November 2020:
- Undertake the second sandfish rescue from lower Biedouw to Enjo Farm dam
- Work with Bushmanskloof to create a second sandfish nursery dam
- Continue monitoring at sites in river and farm dam.
- Mark recapture study in the gorge using elasmer markers”
For more information or to be part of this exciting project, please contact Jeremy Shelton on: firstname.lastname@example.org