Marine Institute

Our People – Jonathan White

In 2021, the Marine Institute is profiling our people, sharing their study and career paths, the work they do at the Marine Institute and the important contribution their work delivers.

Jonathan White, Marine InstituteJonathan White
Team Leader, Demersal Fisheries
Marine Institute

What is your current role at the Marine Institute and what's involved in your daily work?
My role is to provide independent, objective advice on the state of demersal fish stocks through a scientific approach.
I'm lucky to work with a great group of dedicated scientists assessing the state of demersal fish stocks (a species within a defined sea area), including crustaceans (Dublin Bay prawns), seafloor dwelling (plaice, sole, megrim, monkfish, skates and rays) and "round" or "white" fish that live close to the seafloor (cod, haddock, whiting, hake, pollack, saithe).
We collate catch data, observations from fishing boats and ports, and undertake scientific fishing surveys to quantify catch and biology of stocks (lengths, weights, ages, maturity, sex, health). We review this data to assess how fish stocks are changing and translate this into scientific advice.
Much of my work is undertaken with the International Council for the Exploration of the Seas (ICES). Together with international colleagues we develop statistical stock assessments, reviewing the biomass (stock size) and fishing pressure of stocks against reference points, and advise on future catch quantities based on the precautionary approach and maximum sustainable yield principles. There's a lot of reviewing and translating this into advice for stocks across the north east Atlantic.
This all feeds in to the Marine Institute's Stock Book, an annual review of the state of fishing and fish stocks of national importance and their environment.
ICES advice informs the EU's Directorate-General for Maritime Affairs and Fisheries (DGMARE) on proposing annual Total Allowable Catches (TACs). The Stock Book advises Ireland's Department of Agriculture, Food and the Marine (DAFM) on the background to ICES advice and context of DGMARE's proposed TACs.

What did you study and why?
From an early age, I was fascinated with water and ecology, plants and animals living in it, mostly in streams. The what, where, why and how it all fits together, pointed me towards science in school and on to University. A Degree in Science and the Environment, where I realised studying ecology really requires application of statistics, lead to a Master's degree in Natural Resource Management focusing on river ecology, invertebrates and bio indicators, and needing statistics. After a year working in a freshwater laboratory I undertook a PhD researching potential use of invertebrates to indicate ecological quality of Irish lakes and more statistics. My interests at this stage were multi-species assessments, abundances and distributions, associations with water chemistry, habitat diversity and complexity – ecological scales, patterns and processes. With these I began in the Marine Institute on fisheries and oceanography, then moved into seafloor habitat mapping. I worked on statistics of national and international salmon stock assessments before demersal fisheries, stock assessments and advice.

What are you interests and passions?
Scuba-diving, there's nothing better than exploring remote coastlines and the world below the water. These days a walk by the sea will do, it's amazing to watch, and I still want to get in and have a look around.

What is the best thing about working in the Marine Institute? What do you enjoy most about your job?
I love what I do. I work with a great group and the subject keeps me continually curious, learning and developing. Ecology is the study of many elements in continual change. It's not like classical science where a "control" can be run in parallel to an experimental situation to compare and examine effects. We are continuing to learn how fish stocks are affected by their environment, how we can best monitor and predict them. Early amazement from watching minnows and pond-skaters in small streams is still with me, "where are those two-year old fish, what are they eating, what's eating them, how fast are swimming and growing, are they following oceanographic fronts, depth profiles, how does weather effecting their spawning..." it's just on a much larger scale than the stream I stood in at the end of the allotments.

What is something you think everyone should know about the ocean?
• A wave moves forwards; the water it's made of doesn't.
• Cold water can contain more dissolved oxygen than warm water and therefore cold water can support more life.
• Water is heaviest at 4°C, so a hotter or colder layer can sit on top, it's why ponds don't freeze all the way down and why fish can be found hiding in the bottom of pools in the heat. The water there will be warmer/ or colder and contain more oxygen.
• Many juvenile fish migrate up and down in the water column diurnally (by day and night), and are moved passively horizontally by different oceanic currents at different depths.
• Statistics are amazing, they don't have to be difficult, it's the way they're taught that can make them seem so.