By Paul Humphries
Recently, I co-supervised an Honours project by Casey Shaw, together with Keller Kopf at Charles Sturt University. Casey’s project investigated the reasons why small-bodied freshwater fishes tend to be over-represented in the IUCN’s red list: species at risk of extinction. Unlike marine fishes, and unlike many other vertebrate groups, if you are a freshwater fish, the smaller you are, the more likely you will suffer at the hands of inconsiderate human-induced change. What she found was very interesting, but that is for another time. What she didn’t find, however, was even more interesting, albeit disturbing, and has prompted the subject of this perspective article: the need for basic biological knowledge on freshwater fishes.
Casey found enough basic life history and habitat information for only 204 species from four river basins (although she started off wanting to include seven), which was about half of the total number of species present. In another example, in our recent chapter on reproduction and early life history of Australian freshwater fishes (King et al. 2013), we were only able to find 53 species for which the absolute basic life history knowledge (egg number, egg size and length at maturity) was available. This is only about 20% of the total Australian freshwater fish fauna! There were also only 20 species for which there are good, solid length-egg number relationships determined in the published literature. And if you think that the parlous state of our knowledge of the biology of Australian freshwater fishes is because of all the under-studied northern tropical species, you’d only be half right. There are many, many species in southern Australia for which we have little detailed biological information. Most well-studied species are those important for recreational fisheries. For something as basic as diet, there is a real gap in our knowledge of what fish eat, how much, when and where they get their food and how this translates into growth, reproduction and survival. And what is equally worrying, is that once one person has described the diet of a species in one location at one time in history, the rest of us assume that that is what they eat throughout their distribution and for all time! Or at least that is the implicit assumption, considering repeated dietary studies are as rare as (if you will excuse the pun), hen’s teeth.
Ripe Galaxias truttaceus (Photo courtesy of Paul Humphries)
But why should we care about this sort of basic biological information? Isn’t it all a bit dull? It certainly won’t get you far as a new researcher and many of your colleagues, especially the modellers amongst them, will look down their perfectly-formed noses at you with disdain (although it is your data that they will be asking for to populate their models, so there!). Well, we should care. A recent paper by Tewksbury et al. (2014) has highlighted the reasons why ‘natural history’ (“…the observation and description of the natural world, with the study of organisms and their linkages to the environment being central”, Tewksbury, 2014) is absolutely vital for all sorts of reasons: human health (about 75% of emerging diseases are associated with animals, and some of the biggest killers in human history, like malaria, have animal vectors); food security (e.g. the associations of crops with pollinators and pests, understanding what factors influence fisheries); conservation and management (how are we to conserve a species without knowing where it lives, what substrate it spawns on and what eats it?); and recreation (hunting and fishing are some of the most popular pastimes there are, and understanding what may happen if you introduce a new species or food item to an existing sport fishery can be the difference between success and abject failure).
Paul with an even riper Murray cod!
Unfortunately, as I have alluded, and as Tewksbury and colleagues point out, natural history is on the decline. And it is relatively rare for Honours or postgraduate students to do straight natural history type projects. But it is what we need! If I had a challenge that I would throw to all fishy types out there who care about such things: it is to work together to systematically document the basic biology of ALL species of freshwater fish in Australia. But that is a big task, and one that would take a long time to accomplish. Perhaps a more realistic approach would be to assemble a list of species, and knowing what we do about them (even if very little), to place them in categories based on life history (because I reckon that virtually all aspects of a fish’s like flow on from that; that and movement patterns), climatic zone and probably phylogeny (evolutionary relatedness). Then, select a few representatives from each group and focus on those and describe their biology. The aim would be to use those representative species as surrogates for others in the same group, until the others are studied too. Perhaps this has already been done to some extent, but I am not so sure. As the first lot are ticked off, we could expand the species that are studied in each group, which would add to our understanding of how truly representative the first lot are and how much variation there is among species of similar type. Of course, it would be great to include populations of a species from different locations, subject to different pressures and climates, because we know that different stocks may respond differently to environmental variables, such as temperature. But this is ideal, rather than absolutely vital in the first instance.
It is a big job, but I worry that in 20 years’ time, we will be in a worse situation than at present and will be ruing that we didn’t get stuck into it sooner. It will take commitment, tenacity, collaboration, and – of course – funds. But it will save money in the long run….not to mention the species that we love.
KING, A. J., HUMPHRIES, P. & MCCASKER, N. G. 2013. Reproduction and early life history. In: HUMPHRIES, P. & WALKER, K. F. (eds.) Ecology of Australian Freshwater Fishes. Melbourne: CSIRO Publishing.
SHAW, C. 2014. Extinction risk of small-bodied freshwater fishes: the role of functional traits Honours thesis, Charles Sturt University, Albury.
TEWKSBURY, J. J., ANDERSON, J. G., BAKKER, J. D., BILLO, T. J., DUNWIDDIE, P. W., GROOM, M. J., HAMPTON, S. E., HERMAN, S. G., LEVEY, D. J., MACHNICKI, N. J. & DEL RIO, C. M. 2014. Natural History’s Place in Science and Society. BioScience, biu032.
Paul Humphries is an ecologist with a special interest in riverine fishes and their ecosystems. He recently co-edited the book Ecology of Australian Freshwater Fishes with Keith Walker. Paul also maintains a really informative blog at http://paulhumphriesriverecology.wordpress.com/