Why Lake Trout Don’t Need a Calendar


Have you ever wondered why fish spawn when they do? For that matter, how do insects know when to emerge in the spring, or how do birds know when to migrate? As it turns out, two environmental factors largely control the timing these biological processes: temperature and light. Light is more accurately described as something biologists call photoperiod, or the period of time each day between sunrise and sunset.

Did you know that given a day of the year and location coordinates, you can calculate the photoperiod for anywhere on earth? Photoperiod is time spent between sunset and sunrise. The picture above shows Follensby Pond in New York State’s Adirondack Park at sunrise during Lake Trout spawning season.

Imagine a day with little sunlight and cold temperatures. Does winter come to mind? As you probably know, day length is longer in the summer and shorter in the winter. Coupling photoperiod and temperature can be used to predict the time of year. Lake Trout and many other species use these environmental cues to determine when to perform certain life history events. The timing of life history events (such as fish spawning, spring budbreak, insect emergence, etc.) is called phenology.

If light and temperature control the timing of life history events across many different species, what happens if temperature increases with climate change? I have been using historical Lake Trout spawning records and climate data from New York to answer this very question.

Before I delve into the answer, let’s talk a little bit about Lake Trout biology. Lake Trout are coldwater fish; warm water temperatures can cause them great stress, and even warmer water temperatures (< 25ºC or <77ºF), can kill them. Lake Trout are native to Alaska, Canada, and northern regions of the United States. However, climate change is predicted to eradicate Lake Trout from the southern extent of their range and areas of low elevation.

Lake Trout Salvelinus namaycush

Lake Trout generally spawn for two to three weeks from September to November, the timing of which is triggered by cooling water temperatures (8-13ºC) and shortening day length. If the late summer and early fall are particularly warm, it often takes longer for lake temperatures to cool. For this reason, Lake Trout spawn later in years with warm late summer and early fall temperatures, and earlier in years with cool temperatures during the same time period.

This means that if the climate continues to warm, Lake Trout are likely to spawn continually later in time, and populations subject to very warm conditions may stop reproducing altogether due to thermal stress and sub-optimal environmental conditions.

While climate and photoperiod determine the general timing of the spawning period, it’s likely that weather events such as wind storms may trigger Lake Trout to spawn on a shorter temporal scale. Storms are common in Montreal due to the region’s hot and humid weather. I took this photo from the balcony of my apartment.

You might be wondering, “Why should I care about this research?” A few reasons:

     1. Scientists all over the world are trying to figure out how climate change will affect earth’s biology. Research like this adds to the growing body of literature on the sub-lethal impacts of climate change on fish species and other organisms.

     2. If natural Lake Trout reproduction declines, management agencies will need to compensate by reducing Lake Trout harvest or increasing stocking of hatchery-reared fish.

     Recreational Lake Trout fisheries are substantial economic assets. Reducing harvest could also mean a reduction in the economic benefits associated with these fisheries. An increase in stocking could also increase the negative environmental effects associated with fish farming, such as water pollution.

Have I piqued your interest? This research currently comprises the second chapter of my Master of Science thesis for McGill University, and is currently being finalized for journal submission. Read again next month (or perhaps a few months after that, realistically speaking) for more information on the publishing process.

The books that have collected on my desk over the past month of thesis writing. The blue book on top is “Quantitative Fisheries Stock Assessment” by Hilborn and Walters, otherwise known as the fishery science bible.

It’s been over two years since I temporarily moved to Quebec, Canada to pursue a Master of Science in Renewable Resources at McGill University. Last week I submitted the initial version of my thesis to McGill for review. In one week, I move again, this time to the seat of the American revolutionary war: Boston, Massachusetts. Looking back, my time in Quebec has been a blur of traveling for workshops and conferences, pulling fishing nets in the Adirondacks, and long days glued to my computer.

While I prepare to finish, Sarah has decided to prolong her stay in the Netherlands at the University of Groningen to study science business and policy. Congratulations Sarah!

Several undergraduates have asked me for advice on how to get into a natural resource based graduate school program like Sarah and I have been pursuing. The advice from my two year post-undergraduate wizened self is three fold:

     1) Take a modeling class. No, not that kind of modeling.

     A working knowledge of statistical modeling is one of the most useful skills a new graduate student can possess. Already know how to use programs like R, Matlab, or Python? You are way ahead of the game. Many of these programs, like R, contain user guides for beginners, so you can also learn the basics on your own, without taking a class.

     2) Get some field or lab experience.

     Spend a summer or a semester gaining experience as a field or laboratory research technician. There are a lot of important skills to gain outside of the classroom, and there are a lot of graduate students looking for extra help gathering data. While a paid position is obviously preferable, an unpaid position can also look great on a resume.

     3) Do an independent research project.

     This could either be an honors thesis or another project carried out with a graduate student or professor. Want to take it even further? Publish your results in a peer reviewed journal and present at a conference.

Speaking of modeling, I finally caved and ordered myself a Canada Goose parka as a graduation present to myself. It’s one of the warmest winter jackets on the market. Here’s to hoping it curbs the severity of my Raynaud’s (unpleasant but generally nonthreatening circulation disorder) for the upcoming Boston winter.

I have submitted my thesis and finished my course requirements; the congratulations from happy friends and relatives have been pouring in. However, my work here is not yet done. My thesis is now in review, and I will need to address reviewer comments before submitting the final thesis in December. Furthermore, the Follensby Lake Trout management manuscript is back from review and requires modifications in line with the reviewer comments. And on top of that, I am preparing the Lake Trout spawning manuscript for journal submission. With a full time internship, and a substantial list of activities to complete on the evenings and weekends, I will also be searching for a full time job.

In hindsight, those congratulations may have been a little hasty.

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