Conservation Aquaculture and the ‘Cucumber fish’

Our British rivers and estuaries once teemed with life but much was lost due to pollution and flow restrictions in the 20th century. Thanks to European Union legislation, and the work of many incredible institutions to implement it, these habitats are now vastly improved across much of the British Isles. However, some of the incredible species that once dwelled within our rivers and estuaries were lost and will not naturally recolonise without human intervention.

One such species is the European Smelt, Osmerus eperlanus. The European Smelt is an incredible species of fish that is now sadly extinct from many of our river systems. Often called the ‘Cucumber Smelt’ the fish smells incredibly strongly of cucumber and you can often tell when rivers are inhabited by European Smelt by the smell of cucumber emanating from them. This, rather cute looking, fish is relatively small at only about 20-30cm long when fully grown. It is a somewhat pretty fish, with large fins, bright silver scales a often stripes of darker colour running laterally along its dorsal surface. Like Salmon, the European Smelt spends most of its life at sea and only comes into rivers to breed, where it does so on shallow sand banks often many miles upstream. However, quite unlike Salmon the European Smelt does not travel great distances at sea but instead tends to stay local to its native river, often staying close to the river estuary and no more than a few miles along the coast. This is unfortunately the undoing of European Smelt because as various factors, such as pollution (they are very sensitive to water quality), have caused them to become locally extinct from river systems their limited range of travel makes it quite unlikely that a given river should be recolonised by nearby populations should the water quality improve.

The European Smelt, Osmerus eperlanus .

This means that it is required that we must step in and re-introduce them from river systems where they have been lost. As female smelt produce around 40,000 eggs in a single spawning event (typically in the cold months of February to March) it might seem simple to take some of these, fertilize them and simply place them in to the rivers where they are missing. Unfortunately, it is not as easy as that as young Smelt are incredibly vulnerable and ideally, they need to be juveniles or sub-adults if they are to stand a chance of forming a viable population.

Recognising this, the European Union funded the SEAFARE project; a part of which was to tackle exactly this problem – how do you grow European Smelt successfully and in sufficient numbers to make a successful re-introduction program viable? I was employed to take on this research at Bangor University in 2011. So, after designing and building a specialist research aquarium that included various experimental tank setups and all the necessary filtration as well as facilities to grow all the necessary live-food for hungry young Smelt, myself and my colleagues set off to Galloway, Scotland, to collect some Smelt eggs on a cold and wintry day. To obtain Smelt eggs our collaborators at the Galloway Fisheries Trust had caught us some Smelt that had come up the river Cree to spawn. In their hatchery we strip-spawned (which involves gentle massage of the abdomen) male and female Smelt to obtain the necessary eggs and sperm. Smelt eggs are incredibly sticky, which enables them to stick to stones in the river and not be washed downstream by the current, and this presents a problem to us in our experiments so we had to wash them in a slight acid bath to remove their ‘stickiness’. When we returned them to Bangor, we made use of them in various experiments to figure out what the best temperature and salinity was for growing them. We established, for the first time ever, just how embryonic Smelt develop and how fast they grow as juveniles. We ascertained such things as when they transition to various food types and the suitability for different tanks. Would you expect, for example, that juvenile smelt fare best when in blacked out tanks? Clear glass tanks make Smelt fearful and they fight currents in keeping to the corners resulting in lost energy reserves; our answer was to use black plastic wrap to cover all of the tanks and thus make them nice and shady for our nervous baby Smelt.

Dr Nick Jones and I using an acid bath to remove the adhesive surface of our recently fertilized Smelt eggs on a cold February morning in Scotland, 2011

The result of these experiments (and many months of intensive work!) is the recent publication below that details just how to grow Smelt in captivity for conservation purposes. My colleagues, Dr Nick Jones, Dr Ian McCarthy, Dr David Berlinsky and I hope that institutions can use our protocol to begin to reintroduce this amazing fish to places where it has been lost and our rivers can once again smell like cucumber!

Read the publication by clicking on this link below:

Determining the optimum temperature and salinity for larval culture, and describing a culture protocol for the conservation aquaculture for European smelt Osmerus eperlanus (L.)

I’d like to take this opportunity to thank all the people I worked with on this project but in particular the Principle Scientist and my line manager Dr Ian McCarthy. This was my first employment after graduating from my Master’s degree and it was a fantastic start to my research career.


Citizen science & humpback whales

People often assume that science is filled with those ‘Eureka!’ moments. That serendipity is the mother of all scientific discovery. Well, after over ten years of being a marine biologist I can safely say that this is simply not the case, at least not in my experience. There have certainly been some chance discoveries and surprise moments in my career so far, but every single one of these has come after a protracted period of, often tedious, targeted study and painstaking research. It would be very easy to make the ‘eureka’ assumption of the latest piece of research that I have been involved in – the first ever match of a UK humpback whale to Arctic feeding grounds.

Humpback whales, Megaptera novaeangliae, have been found around the UK for as long as humans have walked its shores. Archaeological traces of humpback whale remains have been found in Neolithic sites in the Orkneys and in Bronze Age settlements of the Outer Hebrides1. We should perceive the humpback whale to be as much a part of British wildlife as our magnificent red deer, our secretive badger or even the breath-taking basking shark. Yet somehow it remains firmly in the ‘occasional foreign visitor’ category for most people. Perhaps this is because, throughout much of our recent history, its population has suffered from intense commercial whaling pressure2.

It is maybe because of this induced rarity that the increased sightings of humpback whales over the past two decades has been greeted with such fanfare, often making it in to regional and national media3. In Scotland, humpback whales have been appearing increasingly often, and consistently over the past three years, in the Firth of Forth.  In 2017, thanks to growing awareness of the richness of marine mammal biodiversity in the region, the Forth Marine Mammals (FMM) group was formed. FMM is a community project based around the Firth of Forth that reports live sightings of marine mammals to its members via social media, allowing people to increase their own chance of a sighting and also to share images of encounters.

Since 2017 humpback whales have been appearing in the Firth of Forth between January and March each year. This consistent timing of their appearance soon got local people pondering, “could these whales be the same individuals each year?”, “Where do these whales go when they aren’t in the Firth of Forth?”. Thankfully, owing to the markings found on the underside of a humpback whales fluke, or tail, individuals can be identified in a process known as ‘photo-ID’4 and this can begin to provide an answer to these questions.

The volunteers of FMM quickly became citizen scientists and began trying to match all the incredible photographs of their whales both between years and to whales that had been sighted elsewhere. Facebook, Instagram and Google Image searches were all fair game in their search for potential fluke matches. One incredibly industrious volunteer, Lyndsay McNeil, discovered that one whale, named ‘Sonny’, had visited the Firth of Forth in both 2017 and 2018. This was amazingly important, as it showed that these whales were visiting the Firth of Forth intentionally and that there must be some purpose to their visit. Then, thanks to many hours of work, Lyndsay made another match, this time of a whale sighted in the Firth of Forth in 2018 and in the remote Norwegian archipelago of Svalbard in the Arctic in 2017. This was the first time ever that an individual whale had sighted in both UK waters and its Arctic feeding grounds. The whale was named ‘VYking’ after its distinct Y-shaped marking on its tail.

fluke match
Humpback whale ‘VYking’ as sighted in the Firth of Forth, Scotland (a) and Svalbard, Norway (b). (Image credits: Sandy Morrison/Forth Marine Mammal Project – A, Iain Rudkin/Iain Rudkin Photography – B)

This was a significant discovery and provided an important piece of the jigsaw that is the lives of these incredible marine mammals. Being part of the FMM, myself and my two co-authors, Emily Cunningham and Katie O’Neil, realized the significance of this hard-won discovery and were keen to not only investigate further but to make sure this information was recorded in the scientific literature. We started by confirming the matches with independent viewers, all of whom were experts in cetacean photo-ID. We then sent the best images of all whales individually identified to a wide selection of international photo-ID catalogues to see if any other matches could be made – none came up. Our research into the literature threw up more questions than answers, as is usually the case. Why have the whales only started appearing just recently? Why do the whales come to the Firth of Forth? Where do they head afterwards?

In this post-commercial whaling era, we are seeing many humpback whaling populations recover around the globe5. Unfortunately, we simply do not have the data to know for sure if this is the case for the population we find in UK waters, that of the North-East Atlantic. In fact, we don’t even know if this is a single population as no population genetic studies at an appropriate scale have ever been carried out. I have reason to believe that if such a study were commissioned then it might in fact reveal at least two populations. But if the local population is recovering then that is one possible explanation for their appearance in the Firth of Forth, they could be re-colonizing old habitats or exploring new ones as their population grows. Equally we could be seeing a range shift due to changing environmental conditions, possibly as a result of climate change. For now, and until further data is collected, we simply do not know.

Whale map
Location of independent humpback whale ‘VYking’ sightings (red circles)

Our current level of understanding is also lacking in why the Firth of Forth is so special. It is possible that the improvement in our river systems, as a result of EU directives, has increased the availability of prey fish in the Firth of Forth due to improved water quality, thus making it viable as a feeding area for humpback whales. Again, without further research this is currently guesswork.

Humpback whales are renowned for their extremely long-distance migrations between high latitude feeding areas and low latitude breeding areas6. It is also known that in other parts of the world some juvenile humpback whales either make stop-offs along their migration at ‘service stations’ to rest and feed7 or make only partial migrations to mid-latitude locations8. It is highly probable that the Firth of Forth serves either or both of these purposes. Although the maturational status of the whales observed here is unknown, they do not appear to be fully grown adults and the identification of a nearby stranded individual as a juvenile male adds weight to this idea. Until either new photo-ID matches show up or a satellite tagging study is undertaken we may not know the answer.

We muse about these questions, and others, in our recent publication in Marine Biodiversity Records. This study couldn’t have taken place without all the hard work and dedication of the Forth Marine Mammals group and we want to thank each one of them for their contributions. A personal thank you also goes to my co-authors, for their hundreds of hours of input and for battling through three rounds of peer-review. This is a great example of citizen science and we hope to continue to support them in their discoveries of the secrets of the lives of these humpback whales in the years to come. One thing is for sure, there still remains plenty to be discovered.

The full paper can be found here.


1Buckley, M., Fraser, S., Herman, J., Melton, N.D., Mulville, J. and Pálsdóttir, A.H., 2014. Species identification of archaeological marine mammals using collagen fingerprinting. Journal of Archaeological Science41, pp.631-641.

2Tønnessen, J.N. and Johnsen, A.O., 1982. The history of modern whaling. University of California Press.

3Rare sighting of humpback whale off coast of Cornwall. BBC News. 03/08/2019.

4Wells RS. Identification methods. In: Würsig B, Thewissen JGM, Kovacs KM, editors. Encyclopedia of marine mammals. Academic press; 2017. p. 503–9.

5Katona, S.K. and Beard, J.A., 1990. Population size, migrations and feeding aggregations of the humpback whale (Megaptera novaeangliae) in the western North Atlantic Ocean. Report of the International Whaling Commission (Special Issue 12), pp.295-306.

6Stevick, P.T., Neves, M.C., Johansen, F., Engel, M.H., Allen, J., Marcondes, M.C. and Carlson, C., 2010. A quarter of a world away: female humpback whale moves 10 000 km between breeding areas. Biology letters7(2), pp.299-302.

7Bortolotto, G.A., Kolesnikovas, C.K.M., Freire, A.S. and Simões-Lopes, P.C., 2016. Young humpback whale Megaptera novaeangliae feeding in Santa Catarina coastal waters, Southern Brazil, and a ship strike report. Marine Biodiversity Records9(1), p.29.

8Swingle, W.M., Barco, S.G., Pitchford, T.D., Mclellan, W.A. and Pabst, D.A., 1993. Appearance of juvenile humpback whales feeding in the nearshore waters of Virginia. Marine Mammal Science9(3), pp.309-315.

Ligers, Zorses and Bottlenose Dolphins

Most people do not realise that there are numerous species of Bottlenose Dolphins; the exact number is a subject of strong debate and depending on the background of whom you ask will strongly influence the number they give. For example, a conservationist, a geneticist and a taxonomist are unlikely to agree on such matters. However, there are at least three species formally recognised by everybody, each with their own behavioural and physical characteristics. Of the three recognised species Tursiops truncatus, known as the Common Bottlenose Dolphin, is the species that most people are familiar with. This is owing to it’s near global distribution (it is found in every sea except those in the polar regions), its prevalence in popular culture – be it films or TV and of course its popularity in aquariums during the latter half of the 20th century. The second of the three species, Tursiops aduncus, is more often referred to as the Indo-Pacific Bottlenose Dolphin and as its name suggests is found in the Indian and Pacific Oceans only. Whereas T. truncatus is found in both coastal and offshore environments T. aduncus is principally only found in coastal waters. The third species, Tursiops australis, known as the Burrunan Dolphin is found only in coastal waters of parts of Australia.

One of the most controversial topics in in the field of biology is the subject of what defines a species. Certainly in most high schools, pupils are taught that animals belong to the same species if they can reproduce and form fertile offspring. This is undoubtedly complete fallacy and a recent topic of research that I have been involved in significantly proves this. This research, led by Dr. Tess Gridley of the University of Cape Town, has just been published and I provided the genetics elements included in the paper. The research focuses on the production of fertile hybrids by two species of Bottlenose Dolphin when kept together in captivity. Hybrids are the offspring of two different species – famous examples include the Liger (the offspring of a Lion and Tiger) and Zorse (yes you guessed it, the offspring of a Zebra and a Horse).

Hybrid animals are remarkably common. Here we see a Liger (Lion and Tiger hybrid) on the left and a Zorse (Zebra and Horse hybrid) on the right.

First of all, let’s deal with the elephant in the room. Yes, this research is based on dolphins kept in captivity. Let me be absolutely clear that I am in no way an advocate for keeping any species of cetacean in captivity. When the individual dolphins on which this research focusses were taken into captivity it was the 1970s, at which time our understanding of cetacean biology, in particular their emotional intelligence, was significantly inferior to our understanding today. Like all areas of knowledge, our understanding progresses through time and moral humans adapt their behaviour and actions to take account of this improved understanding. Flipping this on its head, we should be reticent to judge people who made decisions in the past with which we would normally condemn when judging by todays understanding, morality and societal will. Times and understanding were different then and as long as we are willing to, pragmatically and sensibly, adapt our actions today to take account of our improved understanding then we should look forward and not back. No, we should not be taking new cetaceans into captivity but those that currently are kept in aquaria, like those in this study, provide an opportunity to expand our knowledge of cetaceans such that we can continue to improve our decision making in the future; thus, having greater benefit for the conservation of wild cetaceans.

Our research focussed on two dolphins and their offspring. The first, a male Tursiops truncatus by the name of Gambit, and the second a female Tursiops aduncus by the name of Frodo. As well as physical characteristics (Frodo has speckling on her underside, a feature common in older Tursiops aduncus), we confirmed their species identity genetically. This is done using DNA extracted from blood taken from routine veterinary check-ups. The principal finding of this study revealed that hybrid and backcross offspring were fertile – proven by a second generation in both cases.

Backcross fertile
One of the apparently fertile backcross offspring featured in this research.
The underside of Frodo, showing her belly speckling that is a common feature in mature Tursiops aduncus individuals.

This finding is important for two reasons. Firstly, it adds further weight to current scientific thoughts on evolution as a process. We like to think that evolution is a linear process and that once a new species is formed it is permanent until such time that it may go extinct due to some natural disaster or change in environment. We know, however, that this is not the case at all. There are a number of emerging examples that show species emerged in the past, likely as a result of physical separation, but then disappeared again when the physical barrier was removed because they simply merged and interbred with their parent species. A great example of this comes in the form of the Common Raven. We also know that reticulation, or the interbreeding of species during speciation is common and demonstrating the production of fertile hybrid offspring in this study provides a mechanism for this to happen.

Perhaps more importantly, however, this study demonstrates the potential resilience of Bottlenose Dolphins to adapt to changing environments. By producing fertile offspring, the success of gene flow events between different species of Bottlenose Dolphin may allow them to adapt to a more coastal or more pelagic way of life more readily should the need arise. We should take encouragement in this new understanding; although life in our oceans is currently under a great many threats it is likely that, thanks to the plasticity of evolution, the famous smile of a Bottlenose Dolphin will continue to greet us for many generations to come.



This research is published in PLoS ONE, Sepember 2018. You can download a copy of the paper here.

Full paper citation:

Gridley, T., Elwen, S.H., Harris, G., Moore, D.M., Hoelzel, A.R. and Lampen, F., 2018. Hybridization in bottlenose dolphins—A case study of Tursiops aduncus× T. truncatus hybrids and successful backcross hybridization events. PloS one, 13(9), p.e0201722.

Current research

My current research is focussed on developing molecular markers for deep water sharks and is being conducted at Edge Hill University with fellow early career researchers David Goodson, Thom Dallimore and Carl Barker. Deep water sharks are poorly understood relative to their shallow water counterparts but are often even more vulnerable to anthropogenic pressures. Deep water fishing fleets are increasing in size every year and it is well known that many deep water sharks aggregate in single sex or age cohort groups meaning a single trawl can have a very significant impact to localised populations. It is vital that we understand more about these deep water species in order to effectively manage conservation efforts. Key to this understanding is knowledge on population structure and connectivity. The vital first step on this road is the development of molecular markers to enable comparisons.


The shark samples I am working on all come from the Rockall Trough, an area of deep water off the coast of Scotland, and were collected whilst on board the FRV Scotia during a Marine Scotland deep water survey. I am principally targeting the sharks Galeus melastomus and a selection of sharks from the genus Apristurus, including some additional samples very kindly supplied by Dr Ana Verissimo of CIBIO – University of Porto. I am also attempting to replicate the excellent work completed by Helyar et al (2011) who developed microsatellite markers in Centroselachus crepidater. Whilst initial thoughts were to jump straight to population examination through the use of Amplified Fragment Length Polymorphisms (AFLPs) we were encouraged to attempt to develop microsatellite markers by Dr Jim Provan (Queens University Belfast) whilst presenting a poster at the BES Ecological Genetics Group 59th Annual Conference. With his guidance that is exactly what myself, fellow Technician David Goodson and PhD students Carl Barker and Thom Dallimore are now attempting. Please follow me on Twitter for updates and other exciting Marine Vertebrate news.


Helyar, S., Coscia, I., Sala-Bozano, M., & Mariani, S. (2011). New microsatellite loci for the longnose velvet dogfish Centroselachus crepidater (Squaliformes: Somniosidae) and other deep sea sharks. Conservation Genetics Resources, 3(1), 173-176.