Wildlife Wednesday: study finds California sea lions are getting bigger

Plus: juvenile salmon migration timing is changing, candy-striped spiders are catching big prey and $500,000 worth of baby eels seized in Enfield, N.S.

  • May 24, 2023
  • 1,020 words
  • 5 minutes
Male California sea lions are becoming bigger and better fighters as their populations grow. (Photo: Gabriel Tovar/Unsplash)
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From nose to tail, an adult male California sea lion is about eight feet long and can weigh up to 1,000 pounds. However a new study from the University of California Santa Cruz has found that as California sea lion  populations have grown, the males are also increasing in size and becoming stronger fighters.. This finding contradicts the trends seen in other marine mammals who typically decrease in body size as their populations grow. 

Since the Marine Mammal Protection Act was passed in the U.S. in 1972, there has been a notable increase in California sea lion population size, which is currently estimated to be about 300,000 animals along the Pacific coast..Researchers found that male California sea lions — found in the waters of the eastern North Pacific Ocean from Alaska to central Mexico — are becoming larger as their populations grow, while females have remained at a consistent body size. Males also increased their biting force and neck flexibility, making them better fighters. 

During the breeding season, male California sea lions fight aggressively with one another to defend their territories and secure a mate. Researchers believe that due to the greater competition for females, bigger and stronger male sea lions are the most successful at finding a mate and reproducing, thus increasing body size across populations.

Mysterious migration

Different populations of the same species of salmon are responding differently to climate change, based on the timing of juvenile migration. (Photo: Bureau of Land Management Oregon and Washington/Flickr)
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A new study published in Nature, Ecology and Evolution has found that juvenile salmon migration timing is changing unpredictably. Led by Sam Wilson from Simon Fraser University, a diverse group of researchers from across North America compiled the largest dataset on juvenile salmon migration timing, covering 66 populations from Alaska to Oregon. The study found that migration timing in numerous salmon species has changed over the last 20 years due to climate change.

The data demonstrated that different populations of the same species showed greater variation in migration timing than other species. Climate change or geography could not explain the changes in migration timing among these populations. In areas with the same level of warming, some salmon populations migrated earlier, while others migrated at the same time or even later in the year. Additionally, salmon are not changing their migration timing to adapt to changes in food availability in the ocean.

Due to the unpredictable nature of salmon migration timing, salmon conservation and habitat protection is essential. As climate change alters their ecosystems, salmon populations become more vulnerable. Understanding and predicting how salmon populations respond to climate change will help researchers determine conservation priorities.

Misleading macroalgae 

Seaweed growth can be misleading and hide the impacts of human activity on the coral reefs that lay underneath. (Photo: Ronile/Pixabay)
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For some, it might be easy to walk past seaweed along a shoreline and not think twice about what its presence, or lack thereof, means for the surrounding ecosystem. That is unless you are studying coral reefs.

Seaweed, also known as macroalgae, is a group of multicellular, non-flowering, aquatic plants that exist throughout ocean ecosystems. Since the 1970s, scientists have assumed that human activity increases macroalgae growth while damaging the coral reefs that lay underneath. Because macroalgae is relatively easy to access and measure, it has long been used to estimate the impacts of human activity on coral reefs by scientists. But a new UBC study has found that seaweed can be misleading. 

Researchers have found that not all seaweed species respond to human activity the same way. While some species of seaweed grow more in water contaminated by human activities, others are less likely to grow in the same environment. Therefore, depending on the species, areas with less seaweed growth may have unhealthy coral reefs underneath. 

Relying on seaweed to show signs of human activity may hide the damage we cause to coral reefs and prevent scientists from implementing conservation measures to protect them.

A fishery gone wrong

Baby eels or elvers are caught in the Maritimes and sold for up to $5000 per kilogram. They are then shipped to Asia where they are grown for food. (Photo: U.S. Fish and Wildlife Service Northeast Region/Flickr)
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A fisheries officer has seized $500,000 worth of baby eels in Enfield, N.S., in the wake of the commercial elver fishery closure in Nova Scotia. The baby eels — also known as elvers — weighed 113 kilograms and were seized along with a truck, trailer and $15,792 in cash. The person associated was arrested. 

Licensed elver fishers in the province are currently unable to fish due to a 45-day shut-down of the Maritime elver fishery that started on Apr. 15. The Federal Fisheries and Ocean Minister Joyce Murray authorized the shutdown in response to illegal poaching that has led to violence and overfishing. Though the shutdown has kept licensed fishers out of Nova Scotia waters, it hasn’t stopped illegal harvesters from fishing and selling elvers on the black market. 

The Atlantic Elver Fishery has set up trail cameras in rivers south of Halifax and says that several metric tons of elvers have been illegally harvested since the shutdown. The fishery wants the Department of Fisheries and Oceans to do more to prevent illegal elver harvesting, which harms both the commercial fishery and the Indigenous people who exercise their treaty rights to harvest elvers.

Bitter sweet spiders

Candy-striped spiders can take down prey much larger than themselves, including unsuspecting sleeping pollinator species. (Photo: Martin Cooper/Flickr)
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Candy-striped spiders are known for their eye-catching candy-like colour, but a new Ecology study has made some concerning findings about its impact on pollinator species. The study — conducted by researchers from the University of Toronto and McGill — found that these web weavers are capable of taking down prey much larger than themselves, including sleeping bees and wasps. 

Candy-striped spiders were accidentally introduced to North America in the early 1900s and have since become common. Despite numerous studies on the genetics behind its colour, very few studies have examined this species’ behaviour and diet. 

Climate change and human activity has led to the decline of important pollinator species that contribute to the health of their ecosystems. By preying on pollinators like bees and wasps, the candy-striped spider poses a threat to many North American ecosystems. However, these spiders are a sweet find for farmers, as their diet makes them a useful form of pest-control. Now, researchers plan to study these species’ role in agroecosystems to determine if the sweet effects of their pest-control abilities outweigh the bitterness of the threat they pose to pollinator species. 


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