May or May Not include Mammals

Monday-Friday at 8:00 am PST

Hello!

Welcome to fishenjoyer1, this blog is run by Sabrina! (She/her, it/its). my main blog is @imthatwannabeauthor I am currently in college receiving a degree in Biology for transfer to Marine Biology, and a big aquatic enthusiast.

I post about animals that live in the water. 👍

Please visit my website archiving my Fish of the Day posts!

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Today's fish of the day is the Mexican Tetra!

(image source: Wikipedia https://en.wikipedia.org/wiki/Mexican_tetra) 

The Mexican tetra, Astyanax mexicanus, also known as the blind cave tetra, is a freshwater fish known for their surface dwelling, and blind cavefish forms. These fish are found throughout subtropical America, in Southern Texas and New Mexico, and Northeastern Mexico. Along the Rio Grande, Nueces, and Pecos rivers. Living over gravel and sandy regions in mid to shallow moving waters. Waters must range from 68-77°F or 20-25 °C, and fish will migrate south to warmer waters when temperatures decrease in winter.

(image source: Denver Zoo, https://denverzoo.org/animals/blind-cave-fish/)

Blind cavefish are shaped by the pitch black caves they live in, losing their silver color and turning albino-esc pink, and losing their eyes. The degree of eye loss relating to the amount of light present in their environments. Despite this characteristic eye loss, the blind Mexican tetra can continue to react to light when introduced. This is due to a pineal eye, light sensing nerves that wire into the brain separate from the eyes. However, this pineal eye is primitive, only able to tell shadow from light, and unable to sense finer details. The loss of vision has little effect on the tetras, with the lateral line sensing organs becoming particularly sensitive, and a heightened nervous system. This allows for both an extraordinary sense of smell, as well as slight echolocation. Blind cavefish can be found in 3 major cave regions, around 30 living populations, with DNA testing showing that Mexican tetra surface dwellers have entered and adapted to their cave environments on 5, if not more, separate times. This means that different populations of fish have undergone regressive evolution uniquely of other cavefish populations, making it all the more fascinating that all populations of cavefish and surface dwelling fish can interbreed. 

(image source: fish base, https://www.fishbase.se/photos/PicturesSummary.php?resultPage=2&ID=2740&what=species)

Schooling in groups of several thousand fish, in both the wild, and in captivity these fish are fierce hunters. Growing to a grand total size of 12cm, the Mexican tetra primarily consumes invertebrates. Crustaceans, Arthropods, larvae, and water beetles are common. Aquarium fish are known to bite at the fins of other fish, and occasionally engage in cannibalism. When food supplies dwindle, a common event in cavefish, the diet can be supplemented with algae. Despite their efficiency as hunters, these fish are regularly predated by larger predatory fish. Due to this, these fish can emit an alarm substance, which warns other fish to hide. 

(image source: wikipedia, https://en.wikipedia.org/wiki/Mexican_tetra#/media/File:Epigean_and_cave-dwelling_Mexican_tetras_Astyanax_mexicanus.jpg)

There is no particular breeding season for the Mexican tetra. Male and female fish signal to another interest with erratic and exaggerated gill and mouth movement, likely to sense water movement of another in blind populations. Breeding takes place as the tetras eject ova and sperm well swimming side by side, hiding eggs in crevices. Within 24 hours fertilized eggs will hatch into a larval form. These fry will sexually mature within 6 months, and can live up to 10 years! Interestingly, fish are born with eyes that will later cloud and then shrink due to lack of light in cave populations. 

Sources:

(2013). Retrieved from https://www.qualitymarine.com/news/blind-cave-tetra-astyanax-mexicanus/

(N.d.-a). Retrieved from https://www.fishbase.se/summary/Astyanax-mexicanus

Today's fish of the day is the golden shiner! 

The golden shiner, also known by scientific name  Notemigonus crysoleucas, is an essential North American freshwater fish. Belonging to sub family Leuciscinae, the golden shiner is the only remaining species and genus remaining in the America's, with all other fish in the family found across Eurasia. Within their North American home, these fish can be found in quiet waters. Although these fish can withstand relative turbidity, the golden shiner best thrives in slow moving, heavily vegetated waters. Such as: lakes, ponds, sloughs, and ditches. These environments make for hardy fish, surviving low oxygen, relatively high pH, and most interesting, the highest temperature withstanding of all North American minnows. Surviving up to 40 ° C, or 104 ° F. The golden shiner has a native range across the Eastern United States, and Canada, stretching from as far south as Florida and Texas, to as far North as Quebec, Manitoba, and Saskatchewan. However, these fish are commonly used as baitfish, and are thought to be possibly the most farmed pond fish in the United States, for usage as live bait by anglers. Escaped baitfish has allowed Westward expansion, and populations of invasive golden shiners West of Texas, and the Dakotas. 

Identifiable from other minnows in North America by the deep lateral line dip. A sensing organ that creates dark marks on the side scales of fish, which in North American minnows tends to run relatively straight from eye to anal fin. However, in the golden shiner, the lateral lines dips after the pectoral fins, going as low as the pelvic fins. These fish can also be identified by a fleshy section between the pelvic and anal fins which lacks scales acting as an identifying trait even against other European fish from their sub family, such as the Rudd fish. The diet of the golden shiner is primarily plant based, with fish consuming both phytoplankton and zooplankton regularly in littoral, midwater, and bottom feeding environments depending on abundance. Larger fish are known to consume insects and mollusks as available. This diet allows these fish to reach a maximum recorded size of 14.4in, with most fish remaining 3-8 inches in length throughout their lifecycle. Despite their relatively large size, this does not stop other fish from predating the golden shiner, with bass, bowfin, various birds and snakes regularly hunting. 

Similar to many other shoaling minnows, the golden shiner can release alarm chemicals, which inform other golden shiners about possible threats. A chemical called schreckstoff is stored inside of special skin cells, which release if broken by a predator, informing other fish of dangers. Schreckstoff can survive the digestive process of various predators, and emerges in feces, alarming golden shiners to predator presence. However, even without alarm chemicals used for communication between golden shiners, it's found within shoaling groups that individuals in the front of the shoal dictate movement of groups. Individuals with knowledge on food sources can lead groups, exhibiting memory both in real life, and in laboratory tests. 

Golden shiners can reach sexual maturity anywhere from 1-3 years of age, with northern populations regularly taking 3 years, and southern populations often only 1. Breeding season lasts anywhere from April-October, depending on water temperatures of 15-21 ° C, and female golden shiner's can lay upwards of 200,000 eggs multiple times within a breeding season. These eggs are covered in a sticky coating, and lain in dense vegetation, where they will hatch within 2-4 days. On occasion, golden shiners have been observed laying eggs into the active nests of various predators, such as bass, pumpkinseed sunfish, or bowfins, in an activity called egg dumping. This is similar to some kinds of bird parasitism, where parents of the nest will feed and care for young that are not their own, increasing the chance of survival in species that do not provide parental care. However, in the golden shiner the lain eggs provide no danger or threat to other fry, despite the taking of resources. After these fry spawn, they often form shoals of other young fish, living around littoral zones to avoid predators. These fish can grow up to 4 inches within their first year of life, and often reach 12 inches within 3, growing until death. Their lifespan can reach up to 9 years in cared for individuals, but most survive only 3-6 years. 

Hello fish enjoyers!! I am proud to announce that my college term is wrapping up for the year! With that, the next fish of the day should be coming on June 18th or 19th!

Anyhow, with that announcement made. Is there any chance here anyone in the audience here took the ACS organic chemistry exam... I'm taking it tomorrow, and I'm rather concerned so advice appreciated. After that all I have left is 2 presentations, and 3 more exams, and graduation ceremony on the 18th. So, I sure am excited to go back to learning and writing about fish!

Hello fish enjoyers! So, as you might notice I haven’t posted in a hot minute now, so I suppose I should update you all!

I am officially on the second to last quarter before receiving my associates degree in biology! Should have been one but you know how it is with completion counselors and lying to students about what credits they need,

On that note however, I am proud to announce that I have been accepted at University of Oregon! Go Ducks!

I may be busy, but I should be significantly less busy in the summer!!

Oh! And well I’m here I have a poll for you guys. As of recently, my classes have near exclusively been on chemistry, biological sciences bestie! I may not have much time recently to post about fish, but would you folks be interested in posts that are a bit shorter on occasion about other sciences?

Today's fish of the day is the brown catshark! 

The brown catshark, also known by scientific name Apristurus brunneus is a tiny shark around North and South America. Found ranging from British Columbia, down to Baja California, with populations around the Western coasts of Panama, Ecuador, and Peru. This shark is a bottom dweller, living at the depths of 33-1,306 meters, along the continental shelf's lower edge to upper slopes. As these animals stretch closer to the equator, they're found at lower depths, where the waters are colder. Preferential to areas with a sandy, or muddy bottom. 

Brown catsharks, like many catsharks, consume primarily bottom dwelling invertebrates, such as small shrimps, squids, and fish. The behavior of these sharks is relatively non researched, but the brown catshark is believed to be solitary and nocturnal, with possibly migratory populations. Despite being believed solitary, these animals, as a member of the Scyliorhinidae family have excellent sense of smell, and electroreceptors. This gives these sharks the ability to see electricity put off by other animals, and possibly magnetic fields. Helpful, considering it is believed they may be predated on by larger sharks. You can identify these sharks by the short, blunt snout, as well as the blackened edges to the fins. 

Even with little research on the brown catshark, we know that these sharks are oviparous, being the only sharks in the waters off Washington and Oregon state to lay eggs! Only one egg per oviduct, these sharks have tiny litters, with egg cases only 5cm long being carried by the mother from February to August, although some research suggests this may be as long as a year. Pups will be born at 7cm in length, spending their lives alone as solitary animals, maturing at a size of 50cm in both male and female fish, with some sharks getting as large as 68 inches throughout their lifetime, although we don't know their longevity. 

That's the brown catshark, everybody! I hope you have a wonderful Tuesday and expect more fish emails soon! 

Sources:

“Brown Catshark.” OOI Regional Cabled Array, 12 May 2023, interactiveoceans.washington.edu/05/2023/brown-catshark/.

“Species: Apristurus Brunneus, Brown Catshark.” Shorefishes of the Eastern Pacific Online Information System - The Fishes - Species, biogeodb.stri.si.edu/sftep/en/thefishes/species/5269.

“Apristurus Brunneus Summary Page.” FishBase, fishbase.se/summary/Apristurus-brunneus.html.