Where Do Fish Like to Spawn?

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In an effort to explore ways the ocean impacts our lives and the health of the planet, the National Science Foundation (NSF) and Group on Earth Observations (GEO) created a monthly webinar series in 2012 called Blue Marvel ‰ÛÒ Ocean Mysteries. A recent session focused on fish spawning habitat research led by fisheries oceanographer Lorenzo Ciannelli of Oregon State University.

The ocean is home to a diversity of species, almost beyond our comprehension as land-loving humans. It is a place of solace for some, a reminder of the smallness of our petty day-to-day struggles. For others, it is a source of sustenance and income. Regardless of what guides your gaze over the vast expanse of our planet‰Ûªs oceans, one thing is true: We cannot survive without them.

Dr. Lorenzo Ciannelli collecting samples at sea. Image Credit: Lorenzo Ciannelli.

Dr. Lorenzo Ciannelli collecting samples at sea. Image Credit: Lorenzo Ciannelli.

In an effort to explore ways the ocean impacts our lives and the health of the planet, the National Science Foundation (NSF) and Group on Earth Observations (GEO) created a monthly webinar series in 2012 called Blue Marvel – Ocean Mysteries. A recent session focused on fish spawning habitat research led by fisheries oceanographer Lorenzo Ciannelli of Oregon State University.

Organizer Jay Pearlman, an IEEE fellow and founder of J&F Enterprises, notes, ‰ÛÏFish spawning is an integral part of addressing human hunger and food supply. Yet little is understood in detail about how fish select and reuse areas. This is becoming more important with climate change and increasing sea temperatures as fish are quite temperature selective.‰Û

For Ciannelli, the guiding question is ‰ÛÏwhere do fish like to spawn?‰Û He set out to understand whichåÊconditions, like currents and water temperature, limit spawning fish to specific locations and why. Ciannelli looked at several species of fish including Greenland halibut, walleye and Alaskan pollock, and four different types of tuna.

Ciannelli‰Ûªs research is unique, because he merges two perspectives, evolutionary and ecological, to more adequately model spawning behaviors. This new approach could help us to better understand and make more accurate predictions about the impact of climate change on fish and their spawning patterns.

Take Ciannelli‰Ûªs analysis of Greenland halibut as an example of these merged perspectives. From the ecological point of view, halibut spawn in distinct geographical locations in the Bering Sea; they are tied to these locations by their life cycles, predation risks, and access to food. Once the fish spawn, the larvae travel great distances via ocean currents to reach the habitats most conducive as nurseries. During their travels, the halibut larvae grow from eggs into juveniles.

An illustration of walleye and pollack spawning habitats in the Bering Sea. Image credit: Lorenzo Ciannelli.

An illustration of walleye and pollack spawning habitats in the Bering Sea. Image credit: Lorenzo Ciannelli.

Ciannelli believes that fish have a sense of place, quoting author Rebecca Solnit, ‰ÛÏa sense of place is the sixth sense, an internal compass and map made by memory and spatial perception together.‰Û

Ciannelli argues that if the halibut larvae‰Ûªs goal is to reach these nursery areas, a better strategy would be to spawn in close proximity to the nursery areas. Viewed from an evolutionary perspective, he notes that the halibut require the time spent traveling from spawning grounds to nurseries to develop successfully, and this is a genetic process. ‰ÛÏIf you look at the Greenland halibut, you can see the animal has to complete a very complex development and the distance traveled helps that happen over several months,‰Û said Ciannelli.

In terms of climate change, we may assume that these fish will gradually move their spawning habitats toward cooler water temperatures over the next 20 to 50 years.

Ciannelli explains the problem with this approach: ‰ÛÏThe data don‰Ûªt include anything about the evolutionary history of the species. If we go ahead and make this prediction based on that data alone, we could be wrong if we don‰Ûªt account for the fact that the animal has to complete its development as well, and that is not linked to environment. It is linked to the species‰Ûª evolutionary history.‰Û He believes that predictions based only on ecological factors will give us erroneous clues as to how the species may or may not adapt to a changing marine environment.

A satellite image of the region where Greenland halibut spawn in the Bering Sea off of the Alaskan coast. Image credit: NASA.

A satellite image of the region where Greenland halibut spawn in the Bering Sea off of the Alaskan coast. Image credit: NASA.

In the future, Ciannelli hopes to continue gathering information on many more species of fish and their spawning patterns. This data will provide a more comprehensive understanding of the intersection of environmental and evolutionary factors on fish spawning. Expanding this research with richer data will help protect fish populations from overfishing, and offer insights about the best methods for preserving important spawning habitats.

The Blue Marvel series returns in September when Rich Camilli of the Woods Hole Oceanographic Institution is scheduled to discuss his research, which embraces remote sensing and detailed mapping in the ocean environment, robotic vehicle design, and deep-water archaeology. You can catch up on previous webinars in the Blue Marvel archives.