Fisheries scientist at the Marine Institute, Jennifer Doyle has been surveying Nephrops norvegicus stocks, commonly known as the Dublin Bay prawn, for almost 20 years. Growing up close to the River Boyne in Co Meath, Jennifer says she was always spending time outdoors and by the water. “I was always poking around the river, watching the little fish and skaters and catching all sorts of critters hidden around the river,” Jennifer said. “I truly loved biology at school, and my teacher would go into great detail on the plant world, animals and human biology.”
Jennifer’s interest in biology, led her to study a degree in Biology and Mathematics at NUI Maynooth. Fieldwork was a big part of her university experience, and what she enjoyed the most. “Some of my professors were very much in to the outdoors, and would take us on a lot of fieldtrips to collect wildflowers or seaweed species. When you are tramping around beaches, rocky coastlines and fields, it gives you a good feel for whether you like outdoor work. I liked putting on the pair of wellies and mucking about, so I always knew I wanted to work outdoors when I finished my degree,” Jennifer said.
The opportunity to undertake more fieldwork encouraged Jennifer to study a Postgraduate Certificate in Fisheries Management at the University College Cork. Following her studies, she was given first-hand experience working on a commercial fishing trawler in the Celtic Sea.
“On my first trip out to sea, I was very ill for two days. But after I got my sea legs, I actually really liked it. I enjoyed helping out with the sampling and identifying the fish, and being at sea, away from everyday life,” Jennifer said. Jennifer started work with the Marine Institute as an East Coast Observer on the commercial fishing trawlers in the Irish Sea. “I would identify all the different species of fish landings, fish discards, and the non-fish discards and measure these. It was a good grounding in species identification and more importantly working in all sorts of weather and working by yourself as well - you have to be fairly self-reliant and motivated.
I met lots of hard-working fishermen and skippers, working on various trawlers in all types of weather and managed to come back with data sheets full of data,” Jennifer said. After five years working as an Observer, Jennifer secured a position as a Scientific Technical Officer at the Marine Institute focusing on the assessment of the Nephrops norvegicus stocks. Jennifer was part of the team that introduced Underwater TV surveys, a new surveying technique which has now been in use for almost 20 years.
“The underwater TV surveys are a very different type of data collection, because it is a completely dry lab operation and non-intrusive. We use an underwater camera mounted on to a purpose-built sledge, which has lights, navigation sensors, lasers and CTD. The sledge is towed behind the vessel, very slowly at about 0.8 knots to allow detailed examination of the sea bed. The camera collects high-quality image data of the seabed and various metadata.
“There’s a team of six scientists on board the vessel. We work in shifts where we drive and control the sledge to capture the images and then afterwards we review the images identifying and counting the Nephrops burrows and recording other species that we see, such as starfish and crabs.” When Jennifer and her team return from sea, they process all the data collected from the Underwater TV surveys. “We upload the data to our databases and analyse this information using r-scripts. Sampling data is also collected from fishing vessels, such as the sex ratios, weight, mean lengths and other biological details which informs the size structure of the Nephrops population.
It’s really important to have a good relationship with the fishing industry to assist with the collection of this biological data. “All the information collected from the TV surveys and from samples from the fishing vessels is used to accurately estimate the number of Nephrops burrows and mean weights of the Nephrops so we can calculate the total allowable catch each year. The Nephrops landings in 2018 were worth more than €56 million, so sustainable fishing of these stocks is vital.”
The Underwater TV surveys are carried out on the RV Celtic Voyager during the summer months to take advantage of good weather conditions. “Being out at sea during the summer means we can also get to see lots of whales and dolphins. The first time you see a humpback whale or a common dolphin is so special. When the weather is good and the vessel is traversing down the coastline to the next station, it is always beautiful to look back at Ireland’s stunning coastline.
“I think we have a greater awareness about our ocean than ever before. It’s often easy to see the human impact on our land environment, but we sometimes forget that the land is linked to the marine, whether it’s a river, lake or the ocean. We all need to be more aware of our impact on the environment, and respect it – both land and sea.”