MSc Module 5: Aquaculture Production Systems

We just completed a module titled “Aquaculture Production Systems”, which dealt with the more practical, engineering aspects of aquaculture technologies.  The first week we were given lectures by John Bostock, who covered a wide variety of topics including project design and planning, hydraulics, biofiltration, solids removal, sterilization, and processing, to name just a few.  Then, Francis Murray lectured extensively on recirculation systems, which is one area that I feel has a great deal of potential in the pursuit of sustainability.  Finally, Janet Brown lectured on the specifics of mollusc culture, and Colin Hepburn finished off the module with a comprehensive view of seaweed farming and seaweed value chains.

The assessment included a short exam, plus an individual production plan for a hypothetical aquaculture facility.  I chose to do my production plan for a small recirculation tilapia facility, as this is of interest to me and I have some experience designing this type of system.  While the project was immensely challenging and time-consuming, it is invaluable experience into a real-world scenario.

This particular module was important and interesting due to its practicality: additionally, as I am keen on the economics and design of aquaculture operations, this was the first time that we covered materials that I am seriously considering for a career path, so it was great to get this type of exposure.  The next module is called “Aquaculture in Practice”, and includes a 4-day study tour of fish farms along western Scotland!  

MSc Module 4: Genetics and Reproduction

Salmon smolts swimming around a submerged light

We just completed our fourth 2-week module, entitled 'Aquatic Animal Genetics and Reproduction'.  This module was the toughest one yet, but I found the material very useful and applicable.

Herve Miguad was one of the main lecturers, who covered the physiological aspects of fish reproduction, including endocrinology and environmental manipulation for the induction of spawning.  Brendan McAndrew covered the basics of genetic markers and several techniques currently used by the industry to undertake research into concepts such as selective breeding.  Then, Dave Penman lectured on sex ratio control (many farmers may only want to grow one sex of fish, as it may perform better) and chromosome sex manipulation (creating triploid fish- see my previous blog article on triploidy).  We then received a series of lectures on the major biological and practical differences of a variety of finfish hatchery operations, highlighting the ways in which technology conforms to reproductive strategy. 

This module included two field trips: one to Howietown to spawn brown trout broodstock (see my previous blog article), and the other to an Atlantic salmon smolting facility to practice a variety of industry techniques.  'Smolting' is the process that juvenile salmon go through to prepare themselves for the transition from freshwater, where they are born, to saltwater, where they will spend the majority of their lives.  At this smolt unit, owned and operated by the Institute, we practiced blood sampling and performing ultrasounds: the latter is used to determine the development stage of the gonads in large broodstock.  We also practiced inserting PIT (Passive Integrated Transponder) tags into fish: these are tiny capsules that emit a unique ten-digit number when placed next to an electronic reader.  They are inserted just underneath the skin and are used to individually identify fish for the purposes of selective breeding or the establishment of pedigree lines.

Overall, this module was difficult from an academic perspective, but the material seems integral to a comprehensive view of the industry.  The next module is ‘Aquaculture Production Systems’, and as this topic holds a much greater personal interest for me, I am very excited to see what it has in store!

Atlantic salmon smolt next to blood sampling and PIT tagging tools

Using ultrasound to look at the development of the ovaries in a broodstock brown trout

Brown Trout Spawning

Today our MSc class had the incredible opportunity to go back to Howietown, the commercial fish farm owned and operated by the University of Stirling.  There, we saw the hatchery operation and helped the staff spawn their brown trout broodstock.

The broodstock are a population of fish that are kept for breeding purposes.  These are massive fish that have favourable traits that the farmers want to propagate to the offspring.   Under the staff’s supervision, we collected eggs from the females and milt from the males and mixed them together in buckets to fertilize the eggs.  These eggs were then placed in the hatchery, where they will incubate and hatch next spring.

This was an amazing opportunity to get some hands-on experience with spawning broodstock…I will let the pictures speak for themselves!

Expelling the eggs from a female

'Milking' a male- the white fluid is milt that contains sperm

My fish was very ripe and expelled her eggs easily!

Mixing the milt with the eggs completes the process of fertilization

These eggs have been fertilized and will incubate in this hatchery until they hatch in the spring

Sterile Fish Grow Faster and Reduce the Genetic Effects of Escapees

Fish escape from fish farms: this is a known and accepted fact.  Farmers do their best to reduce the risk of escapees, but often they still occur, and the effects that the escaped fish have on the environment is still being examined.  However, it is known that escapees can sometimes breed with wild fish, which can have severe genetic consequences for the wild population.

However, there is a method that can be used to create sterile fish, fish that are physiologically incapable of reproduction: this method is called ‘triploidy’.  Without delving into too much scientific jargon, triploidy involves interfering with the process of fertilization, resulting in an embryo that has more chromosomes than occur naturally.  These fish grow normally, but when they mature and are ready to mate, their gonads do not develop and they are incapable of producing viable sex cells.

This is NOT genetic modification: no genes have been changed or inserted.  Instead, artificial methods have been used to manipulate the number of chromosomes present, resulting in infertility.

But the benefits of triploidy do not stop at sterility: normal mature fish invest massive amounts of energy into gonad production.  In triploid fish, where the gonads do not develop, this energy can be utilized for growth instead of reproduction, meaning that triploid fish grow faster and have better feed conversion ratios than non-triploids: this has large implications for the economic viability of a given fish farm.  Plus, if these fish escape, they are guaranteed to not interbreed and hybridize with wild populations!

From a practical and an economic perspective, producing triploids is not challenging, so more commercial attention should be focused on this practice.  In my opinion, the benefits clearly outweigh the costs, and in an ever-growing effort to become more sustainable, this is a no-brainer for the aquaculture industry.

Cleaner Wrasse: Biological Pesticides to Combat Sea Lice

Cleaner wrasse eat dead tissues and parasites off larger fish

Sea lice are one of the largest challenges facing the salmon farming industry, and current treatment methods to combat these parasites involve chemicals that can have harmful effects on the environment.  However, an answer may be on the horizon: it has been found that cleaner wrasse, a group of fish found naturally all over the globe, have the ability to eat sea lice directly off infected salmon, thus reducing the need for chemical treatments.

In nature, cleaner wrasse form symbiotic relationships with other fish: the wrasse eat dead tissues and parasites off of the fish, which in turn enjoy the benefits of disinfection.  By placing wrasse in salmon cages, fish farmers can help mimic this natural relationship, moving towards more sustainable means of parasite control.

This concept is not new to the industry, but with the increasing pressure from governments and environmental groups to decrease the levels of chemicals used on farms, aquaculturists are taking a renewed interest in the use of wrasse as biological pesticides.  While the introduction of another species into salmon cages has challenges and impacts of its own, the wrasse seem to reduce overall numbers of sea lice and help curb their spread.  Additionally, if they can’t find any lice to eat, it has been demonstrated that the wrasse will start to eat the bio-fouling organisms that settle on the nets, which has even greater implications for improved water flow through the system.

In an effort to shift towards sustainability of operations, wrasse should be more heavily researched and if their benefits mirror the initial studies, their use as biological pesticides should be implemented in salmon farms as soon as possible.