Unraveling the mysteries of spot shrimp
Northern spot shrimp are an important species in Alaska, for commercial, sport and personal use. But in Alaska’s southeast panhandle, their numbers are declining for reasons that are not at all clear.
In the Juneau area, the spot shrimp fishery has been closed to sport and personal use since 2013 due to low abundance. Could warmer and more acidic ocean waters be playing a role?
With funding from Alaska Sea Grant, Sherry Tamone and her team at the University of Alaska Southeast (UAS) are hoping to answer that question, among others. Tamone is a biology professor at UAS, based in Juneau. Her research project, funded by Alaska Sea Grant, examines the early life history and physiology of the Northern spot shrimp (Pandalus platyceros) and how climate change may be affecting them.
“Many communities are interested in the health of this species. We study them because survey data from the Alaska Department of Fish and Game tell us that populations in Southeast Alaska are dropping. Historically there is not that much published or known about shrimp physiology specifically in Alaska,” said Tamone.
Spot shrimp are protandric hermaphrodites, spending the first part of their life—approximately four years—as males before transforming into a reproductive female. Their typical lifespan is seven to 11 years, although direct aging of shrimp is challenging. The first year of a shrimp’s life is risky. The larvae shrimp have to avoid predators, find suitable habitat, and get enough food. In addition to these factors, Tamone is looking at how changing ocean conditions affect the already vulnerable first year of life.
“Early life stages of this species are probably the most susceptible to ocean acidification and ocean warming,” she said. “They rely on calcification to build their exoskeletons when they molt and in a warmer ocean they will need to molt more often.”
If too many shrimp die before adulthood, there won’t be enough breeders and the whole population could be in jeopardy.
In addition to Tamone, the lab team consists of Jamie Musbach, a University of Alaska Fairbanks (UAF) graduate student pursuing a master’s degree in Fisheries, and Mari Fester, UAS undergraduate student majoring in marine biology.
To study the early life history of spot shrimp, Tamone’s team, with the help of the Alaska Department of Fish and Game, obtained adult females carrying eggs, and hatched and reared the larval spot shrimp in her laboratory at the UAS Juneau campus.
How hard is it to raise spot shrimp in the lab? Harder than you think.
“Building a water system to manipulate pH is not easy. Luckily other professors who have built their own are great about answering my questions and are willing to help me out. I’m very grateful,” said Musbach.
Hatchery methods for spot shrimp are sparse, and Musbach spent countless hours perfecting the conditions for growing this species. The larval shrimp hatched out bright orange and were approximately 7mm long. Once hatched, Musbach dedicated herself to caring for the larval shrimp and recording their growth. At the height of the season, Musbach fed her larvae twice a day. As larvae, the shrimp proceed through morphological changes, and with each molt their body shape progressively changes to look like that of the typical adult shrimp. Throughout the larval stages, Musbach recorded growth and noted survivals, identifying important baseline information on the early life stages of this species. Next year, metabolic rates of the larvae will be measured under increased temperature and decreased acidity.
For the 2019 season, the research team will evaluate how exposure to multiple stressors will affect molting biology and metabolism during early life history stages. These factors include temperature and carbon dioxide, both expected to increase in coastal Alaskan waters due to a warming climate and ocean acidification respectively.
The research project is expected to shed light on how these variables affect spot shrimp metabolic rate and ability to molt in a changing environmental landscape.
“Understanding how environmental changes such as temperature and ocean acidification might affect spot shrimp early in life and their ability to survive is important for fishery managers in a time of rapid climate change,” said Musbach.
In addition to looking at metabolic rate, the research team will evaluate stress through a project led by Fester. They will measure heat shock proteins, which are proteins that are expressed when an organism is experiencing stress such as an environmental change. To determine if shrimp are producing these stress proteins, Fester will perform a PCR (polymerase chain reaction) assessment. Coupled with Musbach’s research, Fester will be able to test the metabolic and stress response of spot shrimp to projected environmental changes.
For project details, visit the Metabolic and growth physiology of early life history stages of the northern spot shrimp, Pandalus platyceros page on the Alaska Sea Grant website.
–Written by Maggie Chan