Fish on marine sand: homebodies or adventurers?

fish-3

Word cloud based on the publication text  

A large part of my PhD involves working with researchers from NSW DPI and UOW to try and understand the movement patterns of fishes found on marine sands. And our recent paper (open access and free to read here) on blue-spotted flathead is the first piece of the movement puzzle

“Active acoustic tracking suggests that soft sediment fishes can show site attachment: a preliminary assessment of the movement patterns of the blue-spotted flathead (Platycephalus caeruleopunctatus)”

Paper authors: Fetterplace L, Davis A, Neilson J, Taylor M and Knott N

The Study:

We undertook a preliminary study to assess the movement patterns of the blue-spotted flathead, a common species found on marine sand in coastal waters of south-eastern Australia (see below for some of our underwater footage of this species).

DCIM100GOPRO

A tagged blue-spotted flathead

Why? Well for the most part, we have no idea how fish that live on marine sand move, how far they travel or even if they travel far at all. Sand or soft sediments dominate the ocean floor and make up a large part of the area covered by marine protected areas (MPAs). Without movement data it is difficult to know if a MPA is a suitable size or in the correct location to provide effective protection. Or to identify preferred fish habitat such as spawning or aggregation grounds. Understanding the movement patterns of fish on soft sediments is important to be able to effectively manage fish species found on this habitat.

It is generally expected that on relatively featureless marine soft sediment habitats, such as sand, fish are unlikely to show site attachment or have a home range. In contrast, reef-associated fishes are often found to show high levels of site attachment and may even remain on one small reef outcrop for their entire adult lives.  Its seems a logical assumption that fish on sand will instead move around a lot, as there appears –at least to the human eye–to be nothing to ‘tie’ fish living on sand to one particularly area. One patch of sand looks much like any other to us!

However, there has been little research into fish movement on marine soft sediments to confirm this expectation, with most effort expended on assessing pelagic fish or those found on coral reefs, rocky reefs and estuaries.

The goals of our study were to quantify movement and habitat use of the blue-spotted flathead over sixty days. We would then use this data to help work out where to place tracking receivers to be used in long-term comprehensive tracking of soft sediment fish in Jervis Bay Marine Park, Australia.

Methods

We used acoustic tags to track the fish in the study. Each tag sends out a unique acoustic signal and when this is picked up by a receiver, the fish is ‘detected’. The tags are surgically inserted into the body cavity of the fish under anaesthesia. We then used a portable receiver and hydrophone to follow the fish around and work out where they were over the 60 day study period.

bs-surgery

Top: Bluespotted flathead recovering after surgery. Bottom: Anaesthetised Flathead  being stiched up after undergoing surgery to implant an acoustic tag

jervis-bay-map

The study location in Jervis Bay. We tagged the fish in the top NE region of the Bay and then followed them around for 60 days.

We have also published the data set here and the data is pre-loaded into Zoatrack here, so you can play around with the detection data straight onto maps of Jervis Bay and see how the blue-spotted flathead moved over the 60 day study. It also has a CC-BY license so the data can be freely reused with attribution by other researchers or as examples in classes.

zoatrack-2

The Zoatrack interface allows you to use the data from this study straight away with no login required- check it out here

The outcome:

We found that blue-spotted flathead exhibit two broad movement patterns within Jervis Bay. A majority of fish in this study remained within a small compact area and didn’t move more than a few hundred metres from where they were first tagged; however, a number of fish also made larger-scale movements.

Our study, the first to document the movement of blue-spotted flathead, provides clear evidence of short-term site attachment and compact space use by part of the blue-spotted flathead population in Jervis Bay.  The area used by tagged fish showing site attachment over a 60-day study period was much smaller than no-take sanctuary zones on soft sediments in Jervis Bay Marine Park. However, our results also suggest that part of the population is also non-resident and moves over larger areas. While these results suggest that blue-spotted flathead may respond positively to protection provided by the no-take sanctuary zones in place, further tracking on a larger number of fish is needed to determine exactly what proportion of the population shows site attachment and if it continues over the long term. Lastly, our results demonstrate that if we are to effectively manage fish found on soft sediments we need to revisit the current view that fish on this habitat are unlikely to show site attachment.

What now?

BS

A Tagged blue-spotted flathead about to be released. Note the distinctive tail markings that help identify this species.

The results of this and other studies have  helped in designing the passive tracking array currently in place in Jervis Bay. Using passive receivers allow us to detect tagged fish without the need to be on out the water. Currently there are ~50 of these receivers in place and the “NSW DPI Jervis Bay Tracking Array” is one of the best tracking setups in the Southern Hemisphere.

At present there are a number of tagged soft sediment associated species in the Bay including 48 blue-spotted flathead, 10 Longspine flathead and 17 Fiddler Rays. We have been tracking some of these for over 400 days and will have the results of these long term studies out soon…

Thanks!

Many thanks to the NSW DPI for their support of this project- especially the staff at the Huskisson Office, and to the numerous people that helped out in the field on this project in particular Ian Osterloh, Adrian Ferguson, Mark Fackerell, Matt Carr and Matt Rees. We also thank Duane Byrnes for providing valuable GIS assistance and Margie Andreason for proof reading a number of drafts of the paper.

 

Paper citations:

Fetterplace, LC, Davis, AR, Neilson, JM, Taylor, MD and Knott, NA (2016). “Active acoustic tracking suggests that soft sediment fishes can show site attachment: a preliminary assessment of the movement patterns of the blue-spotted flathead (Platycephalus caeruleopunctatus).” Animal Biotelemetry 4(1): 1-11.

Fetterplace, LC, Taylor, MD, Knott, NA (2016) Data from: ‘Jervis Bay Marine Park: Active Tracking of Blue-spotted Flathead’. ZoaTrack.org. doi: http://dx.doi.org/10.4226/68/5701CE37BD10D

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s