$2.4M (and counting) fish project is poorly-defined & risks ratepayers’ funds

Someone asked me recently why I am so interested in this subject of oyster reefs and “bringing back the fish”.

Right from the very beginning I questioned the absolute need for this investment. This was because of what I was seeing living right on the river, together with the historical data I had read and an absence of any empirical data to conclusively take us all down this path of the so-called Bring Back The Fish (BBTF) Project.

I was left not only confused by the arguments that proponents were making but became more frustrated when, the further that I dug into the subject, the more contradictions and conflicting information I unearthed.

A good example of this which exacerbated the problem for me came when I read a paper by USC’s Ben L Gilby – NSC’s Oyster Bed Trial project manager – titled ‘Seascape context modifies fish respond to restored oyster reef structures’. Gilby wrote that the Noosa River is a subtropical estuary in eastern Australia (~24° S) [supporting] a heterogeneous mix of unvegetated sandy substrate, mangroves (mostly Avicennia marina) and seagrass meadows (mostly Zostera muelleri with leaf lengths 30-40 cm), which contributes to the diversity and abundance of fishes in this seascape (Gilby et al., 2018b).

So if Ben Gilby states the Noosa River has diverse and abundant fish stocks, what is happening?

Subsequently, given that Noosa Shire Council had gone ahead with the trial, I felt that there was an extraordinarily high risk that a lot of public monies would be wasted if the hypothesis around oyster beds in the Noosa River were not scientifically proven out like any experiment over time.

This to me at least is why sticking to the original plan of a three year trial of 14 test sites was – and remains – so critically important. Both NRBF and NSC have recently made very ‘big’ statements about the success of the trials to-date when the evidence is far from compelling.

So, with much opinion based upon anecdote or loosely interpreted data from what can only be described as a dubious interpretation of results, NSC has committed ratepayers to $1.2 million and then some an unknown future amount. (I also note that The Nature Conservancy has been gifted a matching $1.2 million from the soon to terminate Thomas Foundation.)

Why unknown? Well, it’s because we simply don’t know so many things at this stage and we are walking into a commitment that may well see us ‘hooked’ on significant expenditures that may not be economically viable or result in the desired strategic outcomes.

Some of the issues:

• • TNC’s oyster reef projects are all in open water such as Port Phillip Bay, Gulf of St Vincent, Oyster Harbour at Albany, Gulf of Mexico. TNC has no empirical data that correlates directly to an estuarine situation such as the sub-tropical Noosa River and as such they are learning as much as we are. So the obvious question is why don’t the original project managers (University of the Sunshine Coast), which has all the direct local knowledge, finish the three years?
  • TNC charged local authorities for the Port Phillip Bay Oyster Harbour at Albany and the Gulf of St Vincent oyster bed projects some $210,000 per hectare. How many hectares does Noosa optimally need to filter water, remove sediment and pollutants so that we see a measurable positive result? What if we discover that number is so high that we cannot afford it?
  • Then when I read the article ‘Maximizing the benefits of oyster reef restoration for finfish and their fisheries’ by Ben L Gilby, Andrew Olds, et al, I learned that both oysters and individual fish species each have optimal, and often different, physico-chemical envelopes in which they prefer to live.For example, oyster restoration sites must be located within the physiological tolerances of the main reef-building oyster and/or mussel species, with respect to temperature, salinity, dissolved oxygen and turbidity. Catchment run-off, tides, waves and currents also modify these environmental variables over a variety of temporal scales. Therefore, consideration of the range and threshold (tolerances) values of these abiotic factors is more important than their mean values in determining the placement of oyster reefs.In addition, for a self-sustaining bed, the site has to be within a suitable hydrographic regime to get the spat delivered to the area, that is, hydrographic concentration. Selecting sites that match the optimal environmental tolerance envelopes for both oysters and fish should therefore be considered a key goal when seeking to restore fish assemblages around restored oyster reefs. Further reading indicated that different conditions attracted different fish both harvestable and non-harvestable at the trail sites in the Noosa River.
  • In Ben L Gilby’s paper – ‘Seascape context modifies fish respond to restored oyster reef structures’ – it becomes very clear that we have rushed into this partnership with TNC and that our exposure to potentially significant future expenditure is real. Gilby wrote:
    • • • ‘Fish congregate around structurally complex habitats for protection from predation, access to alternate food sources, or to shelter from currents …. these habitats, that include rocky outcrops, log snags, mangroves and seagrasses, are among the first to be removed when humans modify aquatic ecosystems for shipping, shoreline stabilisation, urban development, or fishing activities ….. However, some restoration efforts do not fully consider how the placement of sites……..meaning that the full benefits of restoration might not be achieved’
        • The seascape context of habitats relative to other ecosystems, together with variation in the size and quality of habitat patches, structure the composition of fish assemblages across coastal seascapes (Grober-Dunsmore et al, 2009; Pittman, 2018). For example, the proximity of mangrove, log snags and rocky outcrops to nearby seagrass shapes the composition of fish assemblages across subtropical estuarine seascapes (Gilby et al., 2018b). Consequently, connectivity between ecosystems is now an important consideration in marine conservation planning (Hidalgo et al., 2016; Weeks, 2017).
        • Most studies of the effects of seascape context on the fish assemblages of natural or restored oyster reefs have been conducted in temperate marsh-dominated seascapes, and it is not clear whether similar effects occur in subtropical or tropical seascapes where mangroves dominate (Gilby et al., 2018c). Effects of restored oyster reefs in mangrove-dominated systems, especially in meso- or macrotidal areas, might differ to effects in marsh-dominated seascapes due to differences in mangrove accessibility, food availability, or protection from predators (e.g. Sheaves et al., 2016).
        • Previous research has established that the seascape context ( where a reef is located) of restored oyster reefs can affect both the abundance and diversity of fish in surrounding seascapes.The long-term effects of the placement of restored reefs in different contexts can often be species specific (Ziegler et al., 2018).On occasion, however, fish abundance and diversity is greater on restored oyster reefs that are isolated from other ecosystems, possibly because these isolated reefs provide new, and structurally complex, habitat in locations that were previously low complexity, unvegetated soft sediments (Grabowski et al., 2005; Ziegler et al., 2018), and that reefs placed near other biogenic habitats (e.g. marshes) might not be as effective as isolated reefs for enhancing fish and crustacean abundance (Geraldi et al., 2009).The understandings beginning to emerge from these studies on seascape effects for fish on oyster reef effects have been predominantly built from a narrow geographic range. For example most studies of the effects of seascape context on the fish assemblages of natural or restored oyster reefs have been conducted in temperate marsh-dominated seascapes, and it is not clear whether similar effects occur in subtropical or tropical seascapes where mangroves dominate (Gilby et al., 2018c).Effects of restored oyster reefs in mangrove-dominated systems, especially in meso- or macrotidal areas, might differ to effects in marsh-dominated seascapes due to differences in mangrove accessibility, food availability, or protection from predators (e.g. Sheaves et al., 2016).
        • The principle goal of the Noosa River oyster reef restoration effort is to restore structurally complex habitats and to enhance seascape complexity for fish, including for species of commercial and recreational significance.The composition of fish assemblages also differed among sampling periods, with both fewer fish species and fewer harvestable fishes being recorded on the final sampling event. Sampling period was significantly correlated with salinity; salinity was very low across the entire estuary on final sampling event, following heavy rainfall in the catchment. Therefore, salinity values were not included in subsequent analyses.It was identified in previous research that I found that the four most important criteria for fish abundance and diversity were salinity, water temperature, dissolved oxygen and food availability (fish, oyster and prawns). Yet with the BBTF project these have not and continue NOT to be included. How is this possible?Most estuarine fish species have evolved to cope with variation in the physicochemical properties of coastal waters (Elliott & Quintino, 2007), but are nevertheless also susceptible to extreme water temperatures, salinity levels, and low dissolved oxygen concentrations (Stevens, Blewett, & Casey, 2006) that are beyond their physiological limits.
        • Finally, given the young age of these reefs, fish surveyed in this study were only responding to the actual structure of the reefs themselves, as opposed to any strong benefits associated with food provision from the reefs as the reefs grow, then we could hypothesise that these patterns in augmentation of richness and harvestable fish will simply increase further over time. This, however, will require further investigation.

To summarise, it is all a case of “too late she cried!” – we are blindly going forward with a project that is so poorly defined and budgeted for that if successful will be just pure luck in my view. It is very likely that it will not be defined and proven out (if at all) for at least several years!