Using math to improve fisheries management

 

Our lab uses a variety of mathematical tools to investigate patterns of change in populations of marine fishes and invertebrates. We work at a range of scales, from individual bays and kelp forests to the entire California Current. The overall goal of the lab is to investigate factors affecting the population dynamics of marine fisheries. Essentially, are populations increasing or decreasing, why, and what could we do to manage them more sustainably?

Most of our work uses mathematical models, which are ways of representing the factors causing changes in population size (reproduction, death, harvesting, etc.) using a series of equations. We use those to understand how populations might change if one of those factors changes, and to detect patterns in 'noisy' field data. So, we can ask questions like, "Will restoring degraded habitat rebuild oyster habitat, or do we have to remove oyster predators as well?" or, "Is there evidence of poaching in this marine reserve, based on the number of large fish there?"

The results of our work have been used in a variety of conservation and management processes on the U.S. Pacific, Atlantic, and Gulf coasts. Current research topics in our lab include methods to detect short-term changes in fish populations due to changes in fishery management, the effects of coastal hypoxia on fishery monitoring and management, the role of non-consumptive (fear) effects of predators on fishery populations, and the ability of sea turtles to adapt mating systems to a warming climate.

Research Projects

Marine Protected Areas

Blue rockfish in a kelp forest inside a marine protected area in California. Our group, (primarily postdoc Jess Hopf) uses models to predict how much and how quickly populations should increase after they are protected from fishing in marine protected areas. This information is essential for successful management and evaluation. Photo: Katie Davis

 

Age and Growth of Fishes

Otolith ('ear stone') of a coral reef fish. Otoliths are structures inside fishes' ears that create rings as they grow, like trees. This records both the age and growth rate. Modelers like postdoc Fabio Caltabellotta use that information to predict how quickly fish will get to a certain size. Photo: Will White

 

Oyster Conservation and Restoration

An oyster reef in Florida. Postdoc Laura Storch works with field scientists to understand how harvest, predators, and water conditions affect oyster population sustainability, and how we can restore oyster reefs. Some of this work was featured in a US Supreme Court case over interstate water rights. Photo: David Kimbro

 

Coastal Hypoxia

Dungeness crab fisherman Pat Kemmish with a crab pot mounted with an oxygen sensor. Low oxygen levels ('hypoxia') is a growing problem on the Oregon coast, and can kill fish and crabs. Student Montana McLeod is using these data to understand crab mortality patterns and improve fishery management by accounting for oxygen levels. Photo: Linus Stolz

 

Sea Turtle Conservation

A green sea turtle. A threat facing sea turtles is warming beach sand temperatures because temperature determines the sex of hatchlings. As beaches warm due to climate change, fewer males are hatching. Student Victoria Quennessen is modeling whether and how fast turtles can adapt to warming before going extinct. Photo: NOAA

 

Oceanographic Influences on Marine Species

A late larval stage ('megalopa') of a striped shore crab. Crab larvae spend weeks floating in the coastal ocean, where they are prey for many fishes. Student Jennifer Fisher is studying what oceanographic factors cause shifts in the abundance and distribution of larvae across the continental shelf. Photo: Jennifer Fisher

 

Professor White coauthored this book in 2019. It describes how mathematical models can be used to solve many conservation problems, such as predicting extinction of endangered species or the spread of invasive species.

 

Research Papers and Posters

These are documents meant to give an accessible explanation of some recent research, along with pretty photos in some cases.

Interactive Apps - Give it a Try!

Shiny App
This is an interactive mathematical modeling tool. Users can adjust different aspects of the model, and see how the model predictions change. This gives a sense for how we can use models to solve conservation and management problems. There are two examples. In the first, we use models to decide how to prioritize or rank conservation actions to help loggerhead sea turtles. In the second, we show how models can sometimes lead to unexpected predictions about how populations change over time, and how populations can vary in unexpected ways, even when the environment is constant over time.

Otolith resource
One of the types of data we use in our models relates to the age and growth of fish. This is because we are usually interested in knowing how long it takes a fish to grow to a particular size because bigger fish make more offspring and are more valuable to harvest. We get that information from otoliths, which are hard structures in fishes' ears that accumulate rings like a tree. Just like a tree, one can count the rings and measure the width of them to obtain a record of fish growth. This website shows you what it looks like to 'read' an otolith, and try your hand at it yourself.

Interactive poster about population resilience and marine protected areas.
We use age-structured population models to understand how fished populations respond to environmental variability. In general, fished populations exhibit greater variability than unfished populations, for two reasons: a) they are less dampened by density-dependent processes, and b) reproduction is concentrated into fewer ages, making it more likely that random events will ‘echo’ across generations. In this poster, we share some preliminary analyses examining how no-take marine protected areas (MPAs) could reduce that variability by protecting part of the population from harvest. This is a potential example of how MPAs could provide resilience to environmental variability and climate change.

Interactive poster: Time lags and marine protected area management
We use age- and size-structured population models to understand how fished populations respond to protection inside marine protected areas (MPAs). One generally expects population sizes to increase once fishing stops, but time lags due to demographics and year-to-year variation in larval recruitment can delay those increases. We present several examples of how population models can set expectations for detectable increases in fished populations (and when they may never be detectable).

In the news

 

CONTACT:

Will White, Assistant Professor
HMSC - COMES - Newport Exp Sta
254 Marine Studies Bldg
2030 SE Marine Science Dr
Newport, OR 97365

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