Triple S rated- sex, salmon and scicomm

By Victoria Metcalf 06/03/2015

Milking male salmon- it's all in the hand hold.
Milking male salmon- it’s all in the hand hold.

A long time ago in a place not so far away, a young research scientist spent several weeks each colour-changing autumn ejaculating male salmon for their rich, milky sperm. It certainly wasn’t your everyday job and it wasn’t all as glamorous as it perhaps sounds. In fact it was about as removed from the ivory tower fantasy of academia as possible. And that young scientist was me.

We stood for hours and hours in cold raceway water at the hatchery, with reeking fish-slime infused polypropylene gloves, rubber jacket and lots of layers to keep warm. Forcing oneself to eat sandwiches at lunch with fingers that smelled like salmon. Sitting in an office with the Hatchery lads, entering their male bastion unflinchingly and being eventually accepted I think as they witnessed the hard work we put in and our lack of hierarchy of scientist infiltrators versus hatchery staff. We were all one.

A typical male salmon with its gonads for scale.
A typical male salmon with its gonads for scale.

And the day didn’t end once the males were all spent or used. We might have then to spend some more hours setting up fertilisations with female eggs and some of our milt at the raceway, mixing measured eggs and milt precisely and quickly before putting into tall jars with flowing water.

Then the day went longer still-into the small hours of the morning analysing their sperm on a microscope in the chilled down aquarium back at university. And up again early to do it all again. For weeks.

All of this with two other incredible comrades, the Salmon Sisters we called ourselves- a PhD student and a technician and me.

Having no prior milt stripping experience it was a case of learning rapidly on the job. Field seasons were short and the scale of the study large. Lots of males swimming lazily waiting in a raceway to be netted, gently pulled out of the water, and scanned to identify PIT tags, the unique numerical name they held for each fish.

Getting jars ready for fertilisation experiments
Getting jars ready for fertilisation experiments

Then the salmon hugged close to my stomach. Working out just where to start gently squeezing with thumb and fingers wrapped around their abdomen and then maintain that pressure running from head-end to tail-end was a skill that took time but I got pretty expert at it.

If I did it just right and the male was ripe and ready the white jet of milt flowed forcefully; one of the other Sisters carefully catching it with a plastic pottle until ejaculation ceased. The other Sister sat recording data on a computer at a table next to us. Then when finished, the male got put gently back into the water on the other side of the fence in the raceway.

We called this the “cigarette moment”- the male lying immobile for 30 seconds or so before coming to with a flick of his tail and swimming off- either disgusted or in bliss, who would know?

A precocious male gets milked.
A precocious male gets milked.

The little precocious males were my favourite. So tiny because they mature a whole year earlier and put most of their energy into reproduction, making them squishy testes-filled cuddliness. And they could sure produce a lot of milt when squeezed by my hands. Their strategy is not to win the female but to sneak in when fertilisation is taking place and squirt their milt in adding to the parentage. In the wild, each lot of salmon embryos may have several fathers- alpha male, a beta male or two who also shoot in and shoot their load and precocious or sneaker males.

Unlike humans, fish sperm doesn’t tend to be viable for days. Once that milt hits water, it’s activated and then it only is motile and  swimming madly for 1 minute or so before it runs out of internal ‘steam’. So reproduction for them is a rapid fire  pressure filled act. Chinook salmon have just one breeding season. They might mate (or sneak into a mating act) many times over several weeks but then it’s game over for them.

Unless landlocked, they’re been maturing out at sea, orange fleshed with beta-carotene from the food they have consumed. When it’s their year to mate (usually age 3 or so in New Zealand) they re-find their stream or river of origin and head back up it. Heading from saltwater to freshwater triggers large scale physiological changes. Their digestive system starts to break down and they stop eating.

Most of their remaining energy is then diverted to pumping up those testes. Over the season then, the fish without energy coming in, literally start to decay. Their skin starts rotting and falling off. Handling them to strip them in the last couple of weeks was unpleasant. I do not really eat salmon to this day as a result.

End of season male salmon.
End of season male salmon.

Learning all of this was enthralling. The aim of the research was too- trying to use salmon as a model to better understand the impact that mutations in a special type of DNA (mitochondrial DNA) that organisms have within their cells have on male infertility. This DNA is in a separate location to our chromosomal DNA within something called the mitochondria of every cell.

There could be consequences on the viability of populations, especially endangered ones, of these mutations. This is due to mitochondrial DNA being passed down only from mothers, which means if sperm are affected by a mutation it won’t be selected against and mothers may give the mutant DNA to their sons.

It was just too much exciting information not to share. So I did. I spent some of my weekend nights heading out with my friends to Christchurch bars, where when a guy asked me what I did, I replied “I wank salmon”. Talk about a conversation starter.

If they could get over their obvious shock and take the bait it lead to some hilarious conversations about just what exactly I did and even demonstrations of how to milk a salmon. This was I realise now science communication in a casual setting. I got an awful lot of people excited about salmon sperm and science back then. And my friends still remember those nights with much hilarity and will do so for decades to come.

Science communication takes many forms and next week in the first every #SciCommNZ chat (Wed 11th March 2030-2130 NZT) we will be exploring just that. Such a casual form of scicomm isn’t going to get recognition at present and it’s certainly not going to lead to any awards. However, I think despite being underrated this form of science communication is actually highly important.

Perhaps we should be paying more attention to and training scientists and science communicators for more casual opportunities. Perhaps we should be getting out of our comfort zones and challenging ourselves as I did. Perhaps we should be more controversial and less constrained or restrained.

All of my salmon, sex and scicomm experiences came back to me a few days ago when the wonderful scientist and science communication @Dr_Mel_Thomson started a Twitter conversation that seemed a fitting occasion to dust off the salmon ejaculation stories. That conversation had many of us rolling around the floor in laughter across the world. This tweet in particular elicited a particularly hilarious response.




Let’s value all the forms of science communication out there. Let’s look at how humans interact naturally and tap into that to improve our science communication efforts. A bar may be just the very place to foster science literacy (and not necessarily in a Cafe Scientifique kind of way). And if you can get sex into the science conversation, well that helps too, because sex always sells.

If you want to see the Twitter conversation that spawned (pun intended) this blog post you can find it here.

The conversation lead to a small list of scientists who are engaging in stand-up comedy. They include:

Brian Malow @sciencecomedian

Sean M Elliott @SeanMElliott

Ben McKenzie @labcoatman

Tom Lang @Langaround

Pam Rana

Simon Pampena @mathemaniac

Dara O Briain @daraobriain

Strikes me that there is a shortage of women on this list. Maybe there’s a place for Mel and I after all.

* This post is dedicated to the other two sensational Salmon Sisters, Patrice Rosengrave and Kath McBride, with whom I could not have done this project. Kath very sadly passed away recently. 

The salmon sisters

** The work conducted during this project was supported by the Marsden Fund and my postdoctoral mentor was the effervescent Professor Neil Gemmell who let us all become salmon enthusiasts.

Salmon 2