Hi Ada,

We used unbaited RUVs in mangrove and adjacent habitats to determine whether they would be suitable for fish recruitment in north-western Australia. The water was quite clear in this region, only a report available for now as studies are ongoing (see attached). Marcus Sheaves also has ongoing video based work in mangroves Article Use of mangroves by fish: New insights from in-forest videos

Hi Ada,

The underwater baited video method has also been successfully applied in studies on seagrass meadows (see Jones et. al. 2018), so BRVUS could be used to obtain ‘baseline’ assessments of mangrove associated fish communities where water clarity will permit the use of this technique. Gilby et al (2017) used it successfully in Australian estuaries. In their paper Cappo et al. (2004) showed that changes in fish community structure were comparable between BRVUS and trawl techniques. While BRUVS will not give you the precise measure of fish biodiversity at any one station, they will give you the opportunity to do comparative studies in areas where water clarity will permit. Combining BRVUS sampling with beach seining (or other fisheries-dependent sampling techniques) will give you better results, but for purely comparative studies using BRVUS alone is reliable based on studies done on coral reefs and seagrass systems. If anyone has actually deployed BREVUS in mangrove studies I would really like a reference to that study. Good luck.

Tomas

That's great, I will have a read of Gibly et al 2017 and see if I can use the same techniques in Mangroves. Water clarity will be difficult to obtain in this habitat, but hopefully we will be able to get some nice data and detect fish density variations within sites.

Many thanks,

Ada

Hi Ada,

I forgot to include a must read review paper on underwater video techniques by Mallet and Pelletier (2014), see attached.

Hi Ada,

We used unbaited RUVs in mangrove and adjacent habitats to determine whether they would be suitable for fish recruitment in north-western Australia. The water was quite clear in this region, only a report available for now as studies are ongoing (see attached). Marcus Sheaves also has ongoing video based work in mangroves Article Use of mangroves by fish: New insights from in-forest videos

Michael, thank you for uploading the report and the link to Marcus' paper.

Tomas

Hi Ada,

Whether or not BRUVS are a functional for assessment of fish biodiversity in mangrove systems may also be dependent on the flow rates, flow variability and tide range across the sites being sampled - all of which can be highly variable in estuaries and shallow wave impacted water. If bait plume size varies greatly it will be problematic as the area sampled will be very different at each site. Flow rate will impact on how far away your samples need to be to be independent as well. You could attempt to account for these issues but If you have ok water clarity, then using unbaited RUVS like in Michaels paper and Sheaves et al paper is probably the best bet. Even if you have to do longer deployments and more samples to get sufficient fish on camera.

If you have really low visibility you may not get enough fish on camera on unbaited RUVS though so that could be an issue too - In that case you could use bait, standardise depth of view to whatever the worst visibility is e.g. 1 m or whatever, and then measure the current or flow rate to estimate plume size and/or sample at neap tide or right on dead tide etc to reduce any differences in plume size.

On this front, this paper is worth a read:

Taylor, M. D., Baker, J. and Suthers, I. M. (2013). "Tidal currents, sampling effort and baited remote underwater video (BRUV) surveys: Are we drawing the right conclusions?" Fisheries Research 140: 96-104.

Hi Ada, There has recently been a few published studies investigating fish in Mangroves using both baited and unbaited cameras.

See Benzeev, R., Hutchinson, N., & Friess, D. A. (2017). Quantifying fisheries ecosystem services of mangroves and tropical artificial urban shorelines. Hydrobiologia, 803(1), 225-237.

José Amorim Reis-Filho and Tommaso Giarrizzo have been doing a lot of great research with unbaited and baited camera in mangroves with great results. See

Reis-Filho, J. A., Giarrizzo, T., & Barros, F. (2016). Tidal migration and cross-habitat movements of fish assemblage within a mangrove ecotone. Marine biology, 163(5), 111

and

Reis-Filho, J. A., Harvey, E. S., & Giarrizzo, T. (2018). Impacts of small-scale fisheries on mangrove fish assemblages. ICES Journal of Marine Science.

I am also aware of clear water mangrove work with UVC and BRUVs in the Galapagos that will be submitted for publication shortly.

So, yes it is possible but you really need to be aware of the questions you want to ask and your operating conditions.

Article Inventorying, Mapping and Monitoring of Mangroves towards Su...