Fish Schooled

Tuesday, March 23, 2010

Arrived in Canada

I have safely arrived in Canada. Sorry about the delay in posts. I aim to get back into it tomorrow. I have been here for a week and it is a very beautiful country. Going to live in a new country the second time around is certainly easier, but you just can't escape the feeling of been completely alone, homesickness and of course jet lag. But I am handling it a lot better than last time so these anxious feelings hopefully won't hang around for long. The marine lab I am at is amazing and so is the project. I am very much looking forward to this year. Today I spent most of my day trying to write more grants for more money so I can stay longer. Here are some pics of the place to keep you occupied until tomorrow.

Saturday, February 27, 2010

Are Dolphins Non-Human People?

"Are Dolphins Non-Human People" was one of the questions raised by scientists and philosophers at the meeting for the American Association for the Advancement of Science (publisher of Science). Yes this sounds a little 'tree huggy' even for me, but, upon reading this latest brief in Science I can see the arguments made. This debate couldn't be anymore topical right now with the incident that happened with Shamu at Seaworld in Florida. If dolphins are to be considered as non-human persons then should we be making them do shows and keeping them in captivity?

The first argument of course is the extreme intelligence of dolphins. They (1) have larger brains than humans, (2) have a brain to body weight ratio greater than great apes, and (3) they are the second most encephalized beings on the planet. Encephalisation is the folding of the brain and increases volume and surface area, which has been shown to correlate with intelligence. But intelligence is just one part of the argument. The neocortex of dolphins is very advanced and allows them to problem solve and be self aware, and even have a form of intellect or rational thought. They also have spindle neurons that are involved in emotions, social cognition, and the ability to sense what others are thinking.

Thomas White, a philosopher at Loyola Marymount University, argues that these characteristics makes the dolphin a person, but a non-human person. They are alive, aware of their environment, have emotions, have distinct personalities, exhibit self control, and treat others with respect or ethical consideration. White argues that dolphins tick off all the boxes of what it is to be human. Research on intelligence is still in it's infancy with a lot to discover. But, based on these ideas can we justify putting dolphins in places like Seaworld for our own amusement?

Grimm, D. (2010). Is a Dolphin a Person? Science, 327 (5969), 1070-1071 DOI: 10.1126/science.327.5969.1070-c

Thursday, February 25, 2010

New Postdoc!!

Yesterday I finally got VISA approval and so the last hurdle is jumped. On 15 March I leave the shores of New Zealand and set sail (actually flight) for Newfoundland, Canada, where I will start my new postdoctorate. This will be my home for the forseeable future. How do I feel? I am excited at the new adventure and about getting into a fresh new research project, nervous that I will be able to do it, and sad to be leaving my friends.

it has made me realise what a sacrifice and lonely life a scientist can be. As much as I am glad and appreciative to be going, even if I had wanted to stay in New Zealand I couldn't. Research funding is terrible. I imagine it is better, but not much, in other western countries throughout the world. Thus, you are forced to travel to different locations if you want to succeed. I am single and have few ties to NZ (even though I grew up here) and so it would be much easier for me to travel to a new job than someone who is say in a relationship or married with kids!!!

But on the flip side my friend has the opposite problem. He is a medical doctor and thus can't leave the country even though he is desperate too. I guess its the usual story of you miss what you can't have.

Wednesday, February 24, 2010

What do juvenile mangrove fish want to do when they grow up?

Worldwide, juvenile fish are highly abundant in mangrove habitats and this is especially true for tropical marine ecosystems. Mangroves can act as nurseries to juvenile fish offering protection from predators and a ready supply of food. It has long been considered in conservation circles that such nursery habitats should be protected in order to increase the replenishment of adult fish populations in nearby coral reefs. However, this last idea has actually never been proven, and it could be argued that mangroves act as a sink rather than a source of potential recruits.

Taking a longitudinal approach of following cohorts over time, we evaluated evidence for mangrove-derived replenishment of 10 coral reef fishes by drawing on data from 2 concurrent fish monitoring efforts conducted in Biscayne National Park, Florida, USA, over the period 1999 to 2007. Annual indices of abundance were calculated for fish estimated to be age-0 to 4+ in both habitats, and correlation analyses, with appropriate temporal lags, were performed. Statistically significant (p < 0.05; r2 = 0.30 to 0.71) correlations between juvenile abundances in mangrove habitats and adult abundances on the reef tract 1 to 2 yr later emerged for 4 species: Abudefduf saxatilis, Lutjanus apodus, L. griseus, and Sphyraena barracuda.

This study is novel in that it uses a long term data set > 2 years. It is also one of the few longitudinal studies that matches juvenile abundance with adult abundance in mangrove habitats. The results clearly illustrate that some species spend time as juveniles in mangroves and later migrate to coral reefs. This mangrove-reef ontogenetic connectivity has potential for conservation issues such as nursery habitat assessment and marine reserve design.

Jones, D., Walter, J., Brooks, E., & Serafy, J. (2010). Connectivity through ontogeny: fish population linkages among mangrove and coral reef habitats Marine Ecology Progress Series, 401, 245-258 DOI: 10.3354/meps08404

Tuesday, February 23, 2010

Tracking the wakes of prey

Image: http://www.flower-horn.de

I received a comment yesterday asking about the mechanosensory lateral line. So I thought I would write a post today about one of the really cool behaviours that is mediated by this sensory system. I know this is not a well known sensory system but it is a very important one for fish and aquatic amphibians. The lateral line is a hair cell based sensory system that detects the water movement surrounding the fish. Normally this is to within one or two body lengths. However a recent study has shown that in the European catfish (see picture above) it is involved in the detection of wakes left by potential prey.

Here is the abstract:

Swimming fish leave wakes containing hydrodynamic and chemical traces. These traces mark their swim paths and could guide predators. We now show that nocturnal European catfish (Silurus glanis) locate a piscine prey (guppy, Poecilia reticulata) by accurately tracking its three-dimensional swim path before an attack in the absence of visible light. Wakes that were up to 10 s old were followed over distances up to 55 prey-body lengths in our setup. These results demonstrate that prey wakes remain sufficiently identifiable to guide predators, and to extend considerably the area in which prey is detectable. Moreover, wakes elicit rear attacks, which may be more difficult to detect by prey. Wake tracking may be a common strategy among aquatic predators.

In a later paper the lateral line was ablated and once this was done the fish could no longer track the prey. Thus the lateral line was essential in the tracking behaviour. Although this would have limited functional value in coastal water ecosystems where there is a large degree of water motion, and thus background noise breaking up the wake, this may become more important in still water environments. The catfish in this study is obviously a case in point inhabiting slow flowing or still waters such as lakes.

Image: http://oceanexplorer.noaa.gov

This predation strategy may be even more important in deep sea fish where below 1000m, when vision becomes useless, the lateral line is likely to be the dominant sensory system. In such a hydrodynamically 'noiseless' environment many deep sea fish would be capable of detecting the wakes of prey for up to three minutes since they had passed by. Although this next idea is purely conjecture this may also explain why so many deep sea fishes have rat tails (see pic above). Such a tail would likely result in a much reduced wake!

Hanke W, Brucker C, & Bleckmann H (2000). The ageing of the low-frequency water disturbances caused by swimming goldfish and its possible relevance to prey detection. Journal of Experimental Biology 203(7), 1193-1200
Pohlmann K, Grasso FW, & Breithaupt T (2001). Tracking wakes: the nocturnal predatory strategy of piscivorous catfish. Proceedings of the National Academy of Sciences of the United States of America, 98 (13), 7371-4 PMID: 11390962

Pohlmann K, Atema J, & Breithaupt T (2004). The importance of the lateral line in nocturnal predation of piscivorous catfish. The Journal of Experimental Biology 207, 2971-2978

Monday, February 22, 2010

Big Price For Big Tuna

A tuna has sold for $175,000 in Tokyo's fish market. This is the highest price paid for a fish in nine years. It was caught off the main island of Honshu, which is famed for its high quality fish. It is most likely to end up as Sushi, is this a good sign of just plain luck?

From the BBC

Friday, February 19, 2010

Asocial fish - Coming to a town near you!

A recent paper in the journal 'Proceedings of the Royal Society of London' by researchers at UCDavis have shown that asocial tendencies are crucial in the dispersal of biological invaders, and asocial individuals could lead the invasion front. Researchers investigated the mosquitofish, Gambusia affinis, a small freshwater fish that feeds on aquatic larvae and terrestrial insects trapped at the water surface. The Mosquitofish is identfied by the global invasive species database as one of the most invasive species worldwide invading over 40 countries.

In the study they measured the dispersal ability of different individuals within an artificial stream and compared this to the sociability of the individuals. Sociability was measured as the willingness to shoal. This study is unique in that it investigates within species variation in personality traits whereas most studies undertake comparisons between species.

Their results showed that the distance moved during a dispersal assay was strongly correlated with sociability. Asocial individuals were found to disperse further and more often. In addition, when these same trials were undertaken later the same fish showed similar behaviour indicating that these personality traits are consistent over time. This study highlights that differences in personality traits could have large implications in the invasive process.

This idea is not only restricted to fish. Bluebirds found at the invasion front were also shown to be the most aggressive among their peers. More surprisingly humans also show high dispersal characteristics when asocial personality traits are high. This doesn't bode well for our great discoverers such as Captain James Cook or Columbus. Or those people who colonised the British colonies or moved out west in the USA. Maybe thats why cowboys had such a chip on their shoulder. They really were asocial bastards!

Cote J, Fogarty S, Weinersmith K, Brodin T, Sih A (2010) Personality traits and dispersal tendency in the invasive mosquitofish (Gambusia affinis). Proceedings of the royal society of London: February 19.

Jokela M, Elovainio M, Kivima'ki M, Keltikangas-Ja"rvinen L (2008) Temperament and migration patterns in Finland. Psychological Science 19: 831-837