Author: abby

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 | NOAA Fisheries

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: City of Surrey).

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.

Creel Survey

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A creel survey in action (photo credit: AFS).

Guest post: Logan Neu, University of Minnesota Twin Cities

A creel survey (also known as an angler survey) is a type of in-person survey performed by resource managers where an interviewer asks an angler questions about their fishing experience including questions such as the duration of the trip, how many fish they caught, and if they were satisfied with their experience.  The interviewer may also ask about the angler’s thoughts about a future management decision. Additionally, harvested fish are counted and measured.

Creel surveys are performed to gain insight about recreational angling perceptions, efforts, and harvests in order to inform future decision making.  Creel surveys are a valuable tool for fisheries managers to use in understanding the systems they manage and how the public interacts with them.

phylogeny

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Phylogeny of fishes (diagram credit: evolution.berkeley.edu).

Phylogeny is the representation of evolutionary relationships, often displayed as a “tree” (i.e., branching diagram) where the most closely related organisms are connected by a node and more distantly related organisms have multiple steps back in the tree before they are connected.  Nodes are often characterized by biogeographic events and evolutionary innovations.

In fishes, jawless fishes (such as hagfish and lampreys) are the most primitive, cartilaginous, and without paired fins; sharks and rays are cartilaginous with jaws and placoid denticles; and bony fish are the most diverse and derived fishes, with scales (see cycloid and ctenoid), swim bladders, and bony skeletons.

 

 

Culvert

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Three perched culverts (photo credit: USFWS).

A culvert is essentially a tunnel to pass flowing water, typically a small stream, under a man-made structure, usually a road.  Depending on the size, placement, and design of a culvert, the impacts to a stream channel vary.  These impacts, in turn, can affect fish habitat and fish migration.

Culverts are frequently barriers to fish movement.  If culverts are perched, where the outlet is higher than the elevation of the downstream water, fish are required to leap up into the culvert (if they are able) to continue moving upstream.  Often, culverts are not installed to be perched from the outset, but the situation is caused by erosion at the outlet of the culvert from high flows which scour the channel bed.  This type of culvert creates a downstream pool, changes the flow velocity and habitat type, and, consequently, can alter the fish community as well.

Local, state, and federal managers often work to replace or retrofit culverts that have significant ramifications for fish passage.  The U.S. Fish & Wildlife Service’s National Fish Passage Program is one example.