Nov 132015
 

After a couple of storm related postponements last Summer Brisbane City Council is giving it another go!

If you missed out last year BCC will open Forest Lake to fishing for one day on Saturday, November 21 so that we can remove some feral fish and spread the message about how much of a threat they are to our waterways and native fish species. There's been a surprising amount of interest on facebook so we'd certainly appreciate any members who wanted to come along and help out. It's a unique opportunity for the club to engage with a lot of people we normally wouldn't get to meet. If you'd like to help with putting some of the gear together give Steve Baines a call on 0448890798. Continue reading »

Oct 222015
 

Original story by Tim Stephens, University of California - Santa Cruz.

Scientists investigating ecological consequences of sexual dimorphism and sex ratio variation in mosquitofish populations found dramatic effects.
Mosquitofish have been introduced worldwide as a means of mosquito control. (Photo by Kevin Simon)

Mosquitofish have been introduced worldwide as a means of mosquito control. (Photo by Kevin Simon)

Female mosquitofish are not only bigger than the males, they have bigger impacts on freshwater ecosystems. In a controlled study conducted in experimental ponds, researchers found dramatic differences in pond ecosystems depending on the ratio of males to females in the mosquitofish populations. In ponds dominated by female fish, the researchers observed more pronounced ecological changes, including fewer zooplankton and a greater abundance of algae, than in male dominated ponds.

Mosquitofish, which are often used to control disease-spreading mosquitos, are probably the most widely introduced freshwater species in the world, according to Eric Palkovacs, assistant professor of ecology and evolutionary biology at UC Santa Cruz. They are also listed among the world's 100 worst invasive species by the International Union for Conservation of Nature.

Mosquitofish are known to have detrimental effects on native freshwater fauna, and in a lot of places there are efforts to control and extirpate them. It's been called the 'plague minnow' in Australia and New Zealand because its effects are so drastic," Palkovacs said.

Palkovacs and graduate student David Fryxell are senior author and first author, respectively, of a paper on the new findings published October 21 in Proceedings of the Royal Society B.

Trophic cascade

Female-biased populations (right) reduced water clarity compared to male-biased populations (left) due to the trophic cascade. (Photo by Eric Palkovacs)

Female-biased populations (right) reduced water clarity compared to male-biased populations (left) due to the trophic cascade. (Photo by Eric Palkovacs)

In addition to eating mosquito larvae, mosquitofish prey on other insect larvae, amphibian larvae, and zooplankton such as Daphnia, tiny crustaceans that graze on algae in freshwater ecosystems. Female mosquitofish prefer larger food items than males, have higher feeding rates, and spend more time foraging in the presence of other females. High levels of predation can ripple through the food web in what ecologists call a "trophic cascade." When mosquitofish consume a lot of Daphnia, the resulting trophic cascade leads to an increase in algae.

"Daphnia are the principle grazers in freshwater ponds, keeping algal populations in check," Palkovacs explained. "We found that female-dominated mosquitofish populations cause much more dramatic trophic cascades. When there are more males, the Daphnia population remains higher and algal abundance is lower."

Other effects seen in female-dominated ponds included increased temperature and pH.

Palkovacs noted that many studies have looked at the evolutionary biology of sexual dimorphism (differences between the sexes in traits such as body size or coloring) and variations in sex ratios (when populations deviate from a one-to-one ratio of males to females). But little attention has been paid to the ecological consequences of these phenomena.

"When males and females of a species differ in traits like body size, they might use different resources or interact with the ecological community in different ways. As a result, the species can shape the ecosystem differently depending on the sex ratio of the population," Palkovacs said.

Control strategies

Sex ratios in natural populations of mosquitofish vary considerably from place to place around the world. Furthermore, several of the methods used or proposed for use in controlling mosquitofish populations can lead to changes in the sex ratio. For example, trapping or netting selectively removes larger fish, so would principally target females. "In this case, removing more females than males is a good thing because females have the biggest effects on the ecosystem," Palkovacs said.

Female mosquitofish (top row) are larger than males and often display a distended abdomen due to pregnancy (mosquitofish are live-bearing fishes). Males are smaller, thinner, and characterized by an elongated gonopodium. (Photo by David Fryxell)

Female mosquitofish (top row) are larger than males and often display a distended abdomen due to pregnancy (mosquitofish are live-bearing fishes). Males are smaller, thinner, and characterized by an elongated gonopodium. (Photo by David Fryxell)

Another strategy has been proposed that would involve genetically manipulating the fish so that females only produce male offspring. "The idea was to reduce the reproductive output of the population. Our research shows that this strategy could be doubly beneficial, leading to smaller populations in the long run while also creating more male-biased populations in the short run with less severe ecological impacts," Palkovacs said.

Beyond its practical implications for mosquitofish management, the study highlights an important phenomenon that may be widespread in nature. "Sexual dimorphism is very common, as is sex ratio variation. It's not just a mosquitofish phenomenon," Palkovacs said.

To conduct the experiment, the researchers set up an array of large stock tanks on a level field at UCSC's Long Marine Laboratory. They added sediment and plankton collected from a nearby pond to establish a small freshwater ecosystem in each tank. Mosquitofish were obtained from a California mosquito vector control district, sorted by sex, and introduced into the tanks at five different sex ratios, plus a fish-free reference treatment.

Bird netting kept out birds and mammals that might prey on the fish, but allowed naturally occurring insects and amphibians to lay eggs in the tanks. In the experiment, amphibians laid eggs in all of the treatments, but larval amphibians (tadpoles) were only found in tanks without mosquitofish.

The detrimental effects of mosquitofish on native biodiversity have been widely studied. Sex ratios may play an important role in this, although additional studies in natural settings will be needed to see what the effects of sex ratio variation are in the wild, "in the midst of all the other natural variation," Palkovacs said.

In addition to Fryxell and Palkovacs, the coauthors of the paper include UCSC graduate student Travis Apgar and Heather Arnett and Michael Kinnison of the University of Maine. This work was funded by the National Science Foundation, UC Santa Cruz, and the Maine Agricultural and Forest Experiment Station.

Feb 102015
 

This meeting we'll have two guest speakers who have traveled the state in search of creatures that swim. Both presentations will be an excellent lead up to the Forest Lake Pest Fishing Day on February 21.

Glynn Aland will give us a talk about the feral fish that are invading our waterways. Glynn has worked in a variety of roles with Fisheries Queensland and Seqwater and has conducted fish surveys all around the state.

Glynn Aland at Weary Bay

Gavin Brown will present some turtles from around Australia and take us on a tour of all sorts of turtle habitat. Gavin is a member of Australian Freshwater Turtles (AFT - a non-profit organisation) and has a wealth of experience with keeping turtles and observing them in the wild.

Rare Fraser Island Broad-shelled Turtle, from one of Gavin's expeditions.

The drinks stand and the shop will be open for books and aquarium supplies, and there'll be an auction where members can sell fish, plants, and other aquarium related items. Guests are welcome to come and have a look, you can join up on the night if you're interested.

ANGFA Qld Meetings are held on the second Friday of every other month (even numbers) at the Bar Jai Community Hall, Clayfield, starting 7:30 pm.

Oct 092014
 
Rick Shine says the cane toad's evolution is different to

Rick Shine says the cane toad's evolution is different to "the sort of thing (Charles) Darwin talked about". Photo: James Purtill/ABC News

Original story by James Purtill, ABC News

Cane toads in the Northern Territory and Western Australia have evolved "very very rapidly" to hop in a straight line and cover up to six times more ground than distant cousins back in Queensland, scientists say.

Research published in the Proceedings of the Royal Society of London journal shows "a new kind of evolution" and a phenomenon dubbed "spatial sorting", according to the article's co-author and University of Sydney professor Rick Shine.

"The front has accelerated from about 10-15 kilometres per year to about 60 kilometres per year over the time toads have been in Australia," Professor Shine said.

"To move at that rate, toads have to behave in very strange ways - ways that no other frog has before. Continue reading »

Oct 062014
 

Original story at The Guardian

Spiny damselfish study suggests it would take at least several generations for fish to start coping with climate change.
Spiny damselfish, Acanthochromis polyacanthus. Photo: Flickr/creative commons.

Spiny damselfish, Acanthochromis polyacanthus. Photo: Flickr/creative commons.

Rising carbon dioxide levels in oceans adversely change the behaviour of fish through generations, raising the possibility that marine species may never fully adapt to their changed environment, research has found.

The study, published in Nature Climate Change, found that elevated CO2 levels affected fish regardless of whether their parents had also experienced the same environment.

Spiny damselfish were kept in water with different CO2 levels for several months. One level was consistent with the world taking rapid action to cut carbon emissions, while the other was a “business as usual” scenario, in which the current trend in rising emissions would equate to a 3C warming of the oceans by the end of the century.

The offspring of the damselfish were then also kept in these differing conditions, with researchers finding that juveniles of fish from the high CO2 water were no better than their parents in adapting to the conditions. Continue reading »

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