Kype

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This Sockeye Salmon (Oncorhynchus nerka) displays a spawning kype (photo credit: Ron Harris).

Not to be confused with the popular internet phone/video chat platform of a similar name, kypes are hook like structure that develops on the jaw of some male salmonids during the spawning season.  Though Skype for salmon is still far fetched, this secondary sex characteristic does, in fact, have a role in communicating sexual fitness.

Research suggests that kype size has been linked to spawning frequency, via mate choice (that is, female salmon find a hooked jaw desirable) and competition on spawning grounds (namely, battles between males where the winner gets to pass on his genes).  For repeat spawners with an iteroparous reproductive strategy, the elongated jaw is reabsorbed after the spawning season ends.

Fish conservation zones (FCZs)

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A Fish Conservation Zone (FCZ) located on the Mun River in northeastern Thailand (photo credit: IUCN)

Guest post: Lakshita Dey, George Mason University

Fish conservation zones (FCZs) are areas which are closed off to fishing and other activities in order to protect habitats and restore fish populations. FCZs have emerged as a management strategy in the Mekong Basin to protect and strengthen local communities. These communities benefit by protecting specific areas of water bodies and inland species of fish that reside in the area. 

For more information, please visit: Fish Conservation Zones lead to stronger communities, fewer conflicts and more fish

Amphidromous

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‘O’opu nakea (Awaous stamineus) is an important cultural resource for Indigenous Hawaiians.  All five Hawaiian gobies exhibit amphidromous life cycles.

An amphidromous fish is a type of diadromous fish which migrates between fresh and saltwater.  Unlike anadromous and catadromous fish, which migrate explicitly for the purposes of breeding, amphidromous fish migrate for other purposes.  A typical cycle of amphidromy includes eggs hatching in freshwater or estuaries, larvae drifting out into the open ocean to feed and grow, juveniles returning to freshwater to feed and grow, and adults reproducing in freshwater.  Gobies, such as those found on volcanic islands in the Pacific, exhibit an amphidromous life cycle.

For more information, please see:

And, check out the “CAN YOU SAY ANADROMOUS, CATADROMOUS, AMPHIDROMOUS, OCEANODROMOUS, OR POTAMODROMOUS?” post on The Fisheries Blog!

Cartilaginous

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A Blacktip Reef Shark (Carcharhinus melanopterus) has a fully cartilaginous skeleton (photo credit: David Clode).

If you’ve ever eaten a fish fillet, you’ve probably had the ‘pleasure’ of picking out fish bones from your meal.  While most fish are, indeed, bony (superclass: Osteichthyes), certain lineages of fish have cartilaginous skeletons, meaning that their skeletal structure is composed of cartilage, like a human ear or nose, rather than bone.  Elasmobranchs (sharks, skates, and rays) and chimera (class: Chondrichthyes) have always had cartilaginous skeletons.

 

Atlantic Sturgeon (Acipenser oxyrinchus oxyrinchus) have secondarily derived cartilaginous skeletons (photo credit: NOAA).

Chondrosteans (sturgeon and paddlefish; subclass: Chondrostei) are another group of cartilaginous fish – but with a more complex evolutionary history.  The ancestors of sturgeon and paddlefish had fully ossified, bony skeletons (they are members of Osteichthyes) but they have evolved to have secondarily derived cartilagenous skeletons (i.e., cartilage ➡ bone ➡ cartilage).  They do still retain some bony elements – scutes which are modified bony scales.

 

 

Cetí (Español – English)

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Ceti is the term for post-larvae of the Puerto Rican native S. plumieri (photo credit: Catherine Goodson).

Las comunidades locales puertorriqueñas se refieren al pes nativo postlarva, S. plumieri, como cetí. Las especies de peces de agua dulce puertorriqueña como “dajao,” “gauvina,” y “olivo,” (nombre común del cetí en su fase adulta) son anfidromas. La historia de vida de estos peces incluyen una fase de aqua dulce y marina. En particular, los olivos adultos viven y se reproducen en las partes altas de los ríos, mientras que las larvas derivan río abajo hasta llegar al mar en donde se convierten en post larvas conocidas como cetí (Erdman 1961).Como resultado, grandes bancos de cetí migran río arriba durante el último cuarto de fase de la luna de cadaciclo lunar, de junio a enero en Puerto Rico (Engman et al. 2017).

Durante la migración río arriba, el cetí se enfrenta a altas Corrientes, depredadores, y perturbaciones naturales y antropogénicas. Por esta razón, tiene un disco de succión ventral que le ayuda a sobrevivir  durante el fase adulta y la fase de cetí. El Olivo (nombre común de S. plumieri)  utiliza el disco de succión ventral para escalar cascadas y otras estructuras, como represas (Keith 2003). Por esta razon, también se les llama chupa piedra. El Olivo  hembra puede crecer hasta 103 mm de largo, mientras que los masculinos pueden identificarse por su color azul irredescente. Si van de visita a Puerto Rico, generalmente pueden encontrar al olivo debajo de las rocas en los ríos o millones de cetí que migran río arriba.

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Cetí is a term used by local communities in Puerto Rico to refer to native fish species, S. plumieri, during their post-larvae life history. Puerto Rican native freshwater fish, such as mountain mullet, bigmouth sleeper, and sirajo goby, are amphidromous. Their life histories include both fresh and salt water phases; adults reside and spawn in pools and eddies of the upper parts of rivers, while the larvae drift downstream into the ocean, where they reside until they develop into post-larvae, or “cetí” (Erdman 1961). Schools of cetí locate a source of freshwater and proceed to migrate up stream during the last quarter moon phase of each lunar cycle, from June to January in the Caribbean region (Engmanet al. 2017).

During their migration, cetí, as well as other post-larvae native fish species, compete against high currents, predators, natural disturbances and anthropogenic factors. A trait that aids their survival during their cetí and adult phases is their ventral sucking discs which they use to climb the wet surfaces of waterfalls, rocks and any man-made structure with any type of flow (Keith 2003). For this reason, they have been given the nickname “chupapiedra”, meaning rock sucker. Female sirajo (S. plumieri) can grow up to 163 mm, while males can be easily identified by their blue-ish iridescent colors. If you happen to be in Puerto Rico, you can usually find Sirajo gobies underneath rocks in the rivers or millions of post-larvae migrating up the river mouths.

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References:

Engman, A. C., Kwak, T. J., & Fischer, J. R. (2017). Recruitment phenology and pelagic larval duration in Caribbean amphidromous fishes. Freshwater Science, 36(4), 851-865.

Erdman, D. S. (1961). Notes on the biology of the gobiid fish Sicydiumplumieri in Puerto Rico. Bulletin of Marine Science of the Gulf and Caribbean, 11(1), 448–456.

Erdman, D. S. (1986). The Green Stream Goby, Sicydiumplumieri, in Puerto Rico. Tropical Fish Hobbyist, 34(1), 70–75.

Keith, P. 2003. Biology and ecology of amphidromous Gobiidae of the Indo-Pacific and Caribbean region. Journal of Fish Biology, 63 (1), 831-847.

Mouthbrooding

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Eyed eggs in a mouthbrooder (photo credit: The Fish Room).

Guest post: Gretchen Stokes, University of Florida

Mouthbrooding is when fertilized eggs are carried and incubated in the parent’s mouth.  Rather sophisticated for parental care in fishes, it may have evolved from lack of nest sites, predation or habitat invasion.  It occurs in more than 53 genera of fishes.  Mouthbrooding can be conducted by males (paternal), females (maternal) or both.  While more commonly female, parental care by males occurs in some well-known species, including snakeheads and arowana.  Parental feeding is fairly or fully restricted during incubation, as swallowing or chewing could harm egg development.  Brood parasitism can also occur, where a parasitic fish attacks the brooder’s eggs and leaves behind the fertilized eggs for care by the mouthbrooder (e.g. mochokid catfish eggs incubated in cichlid parent’s mouths).

Fry

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Coho Salmon fry (photo credit: 2020 Santa Cruz Bronson C).

Guest post: Gretchen Stokes, University of Florida

Fry refers to a life (growth) stage of fishes that are recently hatched.  This is generally after the yolk sac has been absorbed and almost or entirely disappeared.  At this point, the swim bladder is typically functional and fish can actively feed for themselves.  Depending on the species, this stage can last a few months or more until scales develop.  Fry can be thought of as the “infant” stage for fishes.  Because of their small size at this stage (often only a few centimeters), fry are vulnerable to predation in this stage and need shallow, protected habitat to feed and grow.

Air-breathing

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A mudskipper is an amphibious, air-breathing fish (photo credit: National Aquarium).

Guest post: Gretchen Stokes, University of Florida

Air-breathing fishes are those that respire using aerial gas exchange instead of, or in addition to, that of the water.  Air-breathing is an ancient vertebrate specialization that evolved from aquatic hypoxia (e.g., areas of seasonally flooded wetlands, under ice).  Air-breathing fishes are equipped with one or more modified respiratory structure to breathe, such as modified air bladders, lungs, skin or gills.  Some air-breathing fishes (facultative air-breathers) rely mainly on gills with supplemental gas exchange from aerial breathing when conditions are poor or it is too costly to obtain oxygen from water.  Other air-breathers (obligate) require continuous, regular surface breathing.  Yet another group of air-breathing fishes are amphibious, venturing to land either in an active or inactive state.

Air-breathing occurs in an estimated 450 species and 49 families of fishes, most of which are found in the tropics.  In North America, common air-breathing species include gar, tarpon and bowfin.  Aquarium enthusiasts may be familiar with the air-breathing habits of well-known betas.  Globally the list becomes expansive with many unique adaptations, such as lungfishes, mudskippers, snakeheads or air-breathing catfishes.  Whether a gulp of air at the water’s surface, crawling on land to feed, or maintaining a high tolerance to air exposure with specialized skin, air-breathing allows for unique adaptations and survival in extreme environments.

Fingerling

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Fingerling size fish (photo credit: Food and Agriculture Organization).

Guest post: Logan Neu, University of Minnesota Twin Cities

Fingerling is a broad term applied to a juvenile fish that is about the size of a finger.  The definition of what length classifies a fish as a fingerling varies between species, but the Food and Agriculture Organization (FAO) generally defines a fingerling as ranging in length from 10 to 15 centimeters.  The term fingerling is most often used in aquaculture and fish stocking programs because fish at this life stage are more physically developed and better equipped to survive the harsh outdoor environment than earlier life stages.  Most fish stocking programs stock fish at this life stage in order to increase the survival rate of the newly released fish.

Substrate

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Substrate in streams, rivers, lakes, and the ocean creates important fish habitat and plays an important role in multiple fish life history processes, daily activity, and prey availability. Substrate in aquatic habitats consists of surface and subsurface materials in the streambed, riverbed, or ocean bottom with different fish preferring different types of substrate.
In freshwater ecosystems, substrate is classified by particle size. For example, boulder is classified as substrate larger than 256 millimeters and very fine sand is classified as substrate between 0.0625 and 0.125 millimeters. Sea grass beds and coral reefs in ocean environments are also a very important substrate for marine fish. Fish rely on specific substrate types for spawning, predation, and shelter. For example, in Moreton Bay in Australia researchers found the double-ended pipefish, eastern trumpeter, and fan-bellied leatherjack all preferred vegetated substrate compared to bare sand substrate.
Changes in substrate can influence growth, survival, and recruitment of fish in aquatic ecosystems. Urbanization, land use, sedimentation, commercial fishing activities, and coral reef bleaching are all factors in shifting substrate habitat with potential negative impacts to fish populations.