Xantic Sargo

It might sound like a make of car, but it’s actually a fish. It does have a cool racing stripe though.

Not to be confused with the swimmer-biting sargo (looking at you, Diplodus sargus!), the xantic sargo instead uses its pharyngeal teeth (at the back of its throat behind the gills) to chomp crustaceans, molluscs, and filter-feeding moss animals known as bryozoans. Not only that, it scrapes its teeth together to vocalise, so it and its wider family are fondly nicknamed “grunts”. You’ll find it shimmering in all its silver glory in the Eastern Pacific, usually flitting about over rocky reefs or near kelp forests, and there’s evidence evolution is working its magic there too.

In their 2005 study, Giacomo Bernardi and Jennifer Lape suggested two populations might be starting to diverge. Between 640,000 and 140,000 years ago, when sargo first flickered its way into the Gulf of California, one group broke off and headed along the northern Pacific coastline. A wodge of land now separates the Gulf of California group from the one on the Pacific side of Baja California, and based on gene analysis, it looks like they’re beginning to evolve separately, so in a few generations’ time, they might not be able to crossbreed. This is known as “allopathic speciation”, and we could be seeing the very first stages in action.

The ones who do breed are “pelagic spawners”, so they fling their eggs about in the water column and let the current and tides carry them away in the spring. In summer, the resulting juveniles are sensibly sociable, forming schools with other fish like salema and keeping close to the shore, their horizontal stripes helping them camouflage (and inadvertently look like burglars).

Even fish have awkward teenage years.

Come winter, it’s off with the baby clothes and time for their black vertical stripe, at which point they mostly abandon their social lives. At least until they hit 5 inches in length – then they’ll join a school of adults, and at 2 years old, it’s time to fling DNA around again! It’s not entirely a free for all though, as distinct couples have been spotted during breeding season.

With its flashy scales, the xantic sargo is a popular sport fish, and is also eaten. Well, less so if it comes from the Salton Sea on the San Andreas Fault, where until 2006, eating more than 114g of fish per fortnight was too risky due to high levels of selenium and other delightful pollutants. Post-2006, women who are pregnant or of child-bearing age are now allowed to eat this amount, but the sargo is far less common in the waters nowadays.

Luckily that’s not the case overall. The xantic sargo is listed as Least Concern, and there’s no indication of a population drop, despite it being a prized catch. That means there’s even more chance of spotting a glamorous gold or albino version. Hooray!

TLDR

Latin: Anisotremus davidsonii 

What? Silver fish with a vertical black stripe

Where? Eastern Pacific Ocean, mainly Mexico and the United States

How big? Up to 58 cm / 1.9 feet long

Endangered? Nope, currently Least Concern, and no indication of population decline.

Probable motto: I lose rather than earn my stripes, but it doesn’t make me any less fabulous.

They look interesting. Do they need my help at all?

Sargo seems to be okay, but its home could do with some love due to pollution, overfishing and acidification:

Conservation International: Pacific Oceanscape

Just to prove I’m not fibbing:

Anisotremus davidsonii“. No date. IUCN Red List of Threatened Species.

Anisotremus davidsonii  (Steindachner, 1876). Xantic sargo“. No date. Fishbase.se.

Austin, Grace. 2017. “Why is this fish biting swimmers at Mediterranean beaches?Times of Israel.

Bernardi, Giacomo, and Lape, Jennifer. 2005. “Tempo and mode of speciation in the Baja California disjunct fish species Anisotremus davidsonii“. Molecular Ecology 14: 4085-4096.

Hastings, Philip A., et al. Fishes: A guide to their diversity. University of California Press.

Moreau, Marie F. et al. 2009. “Selenium, arsenic, DDT and other contaminants in four fish species in the Salton Sea, California, their temporal trends, and their potential impact on human consumers and wildlife“. Lake and Reservoir Management 23(5):536-569.

Observations on fishes associated with kelp beds in southern California“. No date. California Digital Library.

Watson, W., and Walker, H.J. 1992. “Larval Development of Sargo (Anisotremus Davidsonii) and Salema (Xenistius Californiensis) (Pisces: Haemulidae) from the Southern California Bight“. Bulletin of Marine Science-Miami 51(3):360-406.

 

Featured image credit: Muskiebait Adventures

 

It’s my birthday today, so sargo will be my celebratory fish 🙂

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