Glossary of Fish Biology For Marine Wildlife on Tobago Shores

The Glossary of Fish Biology For Marine Wildlife on Tobago Shores is given in alphabetical order:

• A

  • aggression - see behaviour
  • anal fin - the median, unpaired, ventrally located fin that lies behind the anus, usually on the posterior half of the fish.

• B

  • Behavior
    Behavior is the action of a fish in response to its environment including other animals. The most interesting and sometimes the most obvious behaviors involve interactions with other fish. Behavior could be Migration, Schooling, Aggression, Resting, Communication and Cleaning. More details: Fish Behaviour
  • bathydemersal - living and/or feeding on or near the bottom, below 200m.
  • bathypelagic - occurring mainly in open water below 200m, not feeding on benthic organisms
  • benthic - dwelling on, or relating to, the bottom of a body of water; living on the bottom of the ocean and feeding on benthic organisms.
  • benthopelagic - living and feeding near the bottom as well as in midwaters or near the surface. Feeding on benthic as well as free swimming organisms. Many freshwater fish are opportunistic feeders that forage on the bottom as well as in midwater and near the surface.
  • bony fish - having a skeleton made of bone; theses are by far the majority of fish

• C

  • cartilaginous - skeletons made of cartilage, the same flexible material in human ear lobes and nose; these fish include sharks, skates and rays
  • caudal fin - fin that is towards the posterior end, or caudal fin

  • Ciguatera poisoning

    The most common non-bacterial, fish-borne poisoning in the world. It is caused by consumption of reef fish that feed on certain dinoflagellates (ie, algae) associated with coral reef systems. At least 5 types of ciguatoxin have been identified and are noted to accumulate in larger and older fish higher up the food chain. Ciguatera poisoning has been a significant concern in tropical areas for centuries and generally is believed to be confined to coral reef fish in water between the latitudes of 35°N-35°S. In the modern era of world travel and rapid transportation, many warm-water fish are available commercially in markets throughout the world, and cases of ciguatera poisoning may be seen in any location.

    Pathophysiology: Gambierdiscus toxicus is the dinoflagellate most notably responsible for production of ciguatoxin, although other species have been identified more recently. Over 400 species of fish have been implicated in ciguatera poisoning, starting with herbivores and then climbing up the food chain to the larger carnivorous fish.

    Species of fish most frequently implicated include groupers, amberjack, red snappers, eel, sea bass, barracuda, and Spanish mackerel. Fish larger than 2kg contain significant amounts of toxin and readily produce toxic effects when ingested. Although not completely reliable, an immunoassay and mouse biologic assay are available for detection of ciguatoxin in affected fish. Ciguatoxin and other similar toxins are heat stable and lipid soluble; they are unaffected by temperature, gastric acid, or cooking method. Presence of toxin does not affect odour, colour, or taste of the fish.

    Ciguatoxin produces toxic effects by activation of voltage-dependent sodium channels, resulting in hyperexcitability, decreased conduction, and prolonged refractoriness. Effects are most pronounced on neuronal, cardiac, and GI tissues.

    Frequency:

    In the US: Most ciguatera outbreaks in the US occur in Hawaii and Florida, although tourists may develop symptoms after returning home. Global marketing of tropical fish has been responsible for sporadic cases reported across the US mainland.

    Internationally: Annually, an estimated 50,000 cases of ciguatera poisoning occur worldwide; however, this poisoning is difficult to track and is thought to be underreported. Ciguatera poisoning is endemic in Australia, the Caribbean, and the South Pacific islands. No doubt exists that ciguatera has had a substantial economic impact on many of the Third World countries where it is endemic.

    Mortality/Morbidity: Ciguatera poisoning seldom is lethal. Typical mortality rate is 0.1%, although rates as high as 20% have been reported. Death usually is attributed to cardiovascular depression, respiratory paralysis, or hypovolemic shock.

    Race: Several reports note that patients of similar ethnic backgrounds tend to share common symptom groupings.

    Age: Children appear to be affected more severely and are involved more often in life-threatening cases.

    Symptoms and Health effects:

    Currently, ciguatera poisoning is a clinical diagnosis based upon a constellation of symptoms temporally related to ingestion of suspect fish products. Onset of symptoms may be within 15 minutes or as late as 24 hours (rarely) after ingestion of the toxin. Generally, symptoms are noted within 6-12 hours after ingestion of tropical reef fish. Symptoms increase in frequency and severity over the subsequent 4-6 hours. Reported symptoms are numerous but commonly affect 3 major organ systems: GI, neurologic, and cardiovascular.

    GI symptoms often are the first to appear, may last 1-2 days, and include the following:

    • Abdominal pain
    • Nausea
    • Vomiting
    • Diarrhoea

    Neurologic symptoms usually are multiple, varied, and, at times, bizarre. Symptoms may begin within a few hours to 3 days after the meal, can last several months, and include the following:

    • Lingual and circumoral paresthesias
    • Painful paresthesias of extremities
    • Paradoxical temperature reversal (eg, cold objects feel hot and hot objects feel cold); a classic finding, but occurs in only one third of patients
    • Dental pain (teeth feel loose)
    • Pruritus
    • Arthralgias
    • Myalgias
    • Weakness
    • Ataxia, vertigo
    • Respiratory paralysis
    • Coma

    Cardiovascular symptoms are less common but can be severe. They usually resolve within 2-5 days. Patients may experience weakness and dizziness from bradycardia and hypotension.
    Other features include dyspnea, sweating, salivation, chills, neck stiffness, and pruritus.

    Physical Signs:

    Dehydration from GI losses is a common finding.
    Neurologic findings are extremely variable, from mild to life threatening.
    Cardiovascular findings include bradycardia and hypotension. Signs of shock may be observed. Hypotension results from the following:
    Fluid loss
    Bradycardia
    Peripheral vasodilation
    Myocardial depression
    Causes: Ingestion of sufficient quantities of fish with accumulated ciguatoxin produces this syndrome.
    For more detail and treatment - see: http://emedicine.medscape.com/article/813869-overview

  • cleaning - see Fish Behaviour
  • colour- see Fish Colour
  • Countershading- see Fish Colour
  • Camouflage- see Fish Behaviour
  • communication- see Fish Colour

• D

  • demersal - sinking to or lying on the bottom; living on or near the bottom and feeding on benthic organisms
  • depressed - flattened from top to bottom;, like stingrays, they live on the bottom.
  • dermal denticles - most fish have scales but the scales of sharks are called dermal denticles; they are tiny tooth-like structures in the skin that gives the shark's skin a smooth appearance that feels like sandpaper
  • dorsal fin - this fin is towards the back and/or upper part of the body. See Fish Behaviour

• E

  • eel-like - See: Fish Body Shapes
  • electricity - see: Fish senses
  • electrophoresis (electrophoretic analysis - DNA fingerprinting of evolutionary divergence) - the early 20thC gave rise to the concept that chromosomal units called genes are responsible for transmitting heritable information from parent to offspring. The structural and functional properties unique to genes, can be evaluated in a high school laboratory. The process of electrophoresis can be used to investigate various topics in marine biology
  • epipelagic - The uppermost, normally photic layer of the ocean between the ocean surface and the thermocline, usually between depths of 0-200 m; living or feeding on surface waters or at midwater to depths of 200 m.
  • eyes - the eyes of most fish are well developed. Most sharks have pupils that dilate and constrict and they have an eyelid that closes from the bottom upward. Bony fish eyes lack both of these characteristics.

• F

  • fins - they move, stabilise and sometimes protect the fish. A fish may have paired fins (pectoral and pelvic fins), and unpaired fins (anal, caudal, and dorsal fins). Some fish do not have all of these fins, and their placement shows great variability. The very flexible fins of most bony fish have visible supporting rays and spines. The skeletal supports of cartilaginous fish fins are not visible, and these fins are fairly stiff.
  • fusiform - streamlined, fish like the barracuda or jack that are capable of swimming very fast; usually living in open water

• G

  • gills - oxygen enters the bloodstream of the fish at the gills, they are feathery structures found along the sides of the head; the gills of a healthy fish are bright red due to the large amount of blood present. In bony fish the gills are usually covered by a bony plate called an operculum. In sharks there are five to seven gill slits.

  

  • gill slits - in sharks there are five to seven gill slits on the sides of the head which allow water to pass out of the gill cavity

• L

  • lateral line - a sensory organ of fishes which consists of a canal running along the side of the body and communicating via sensory pores through scales to the exterior; functions in perceiving low frequency vibrations and pressure differences in general. Also see senses
  • laterally compressed - flattened from side to side; usually they do not swim rapidly (some schooling fish are an exception). However, they are exceptionally manoeuvrable. Many, like the angelfish, are found near coral reefs. Their shape allows them to move about in the cracks and crevices of the reef. A flounder is a laterally compressed fish that lies on its side on the bottom. Both eyes migrate to the left or right side early in development.
    
  • life support systems - fish need oxygen to survive. Since they do not have lungs they get their oxygen with gills. Oxygen in water passing across the membranes of the gills enters the fish's blood by diffusion. The oxygen that fish 'breathe' is dissolved in the water. It enters the water at the surface by diffusion and as a by-product of photosynthesis by aquatic plants.

    Temperature and salinity are also important. Most fish are adapted to a narrow temperature range. Rapid temperature changes may cause death. Most fish are also restricted to a narrow range of salinity. Freshwater fish placed in salt water, or saltwater fish placed in fresh water may die. Some fish are adapted for life in estuaries where the salinity fluctuates and others, such as salmon or striped bass, are able to migrate between salt and fresh water.

• M

  • migration - see Fish Behaviour

  • mouth

    -
    Sharks' mouths are located on the underside of the head. In bony fish the location of the mouth varies. The location and size of the mouth can be a good indicator of the food a fish eats and where it lives. Fish with large mouths generally eat large food items like another fish; however, the whale shark eats very small organisms which it strains from the water with its huge mouth. Fish with small mouths eat small food items: small crustaceans or molluscs; and, fish with tiny mouths eat tiny things like zooplankton.

    Terminal: Terminal mouth located on the end of the head. These fish chase and capture things, like the tuna, or pick things, like the butterflyfish.

    Up-Pointing: A fish with an up-pointing mouth has a longer extending lower jaw. The mouth opening is toward the top of the head. The tarpon has this kind of mouth. They tend to feed near the surface.
    
    Sub-Terminal: A sub-terminal mouth is on the underside of the head. Fish with this type of mouth usually feed on the bottom. The bonefish has a sub-terminal mouth.
    
    Specialised: Some fish have specialised mouths. The seahorse has a tiny mouth at the end of a straw-like snout that is used to 'slurp' zooplankton.
    

• N

  • neritic: The shallow pelagic zone over the continental shelf; nearshore ocean ecosystems; i.e., those associated with the coasts because the waters are overlying continental shelves and/or the waters are < 200 m deep in areas of coastal submarine slopes

• O

  • operculum - in bony fish the gills are usually covered by a bony plate called an operculum
    
  • oviparous - producing eggs that develop and hatch outside the body of the female - see also viviparous and ovoviviparous
  • ovoviviparous - animals including fish that retain the eggs within the body of the female in a brood chamber in which the development of the embryo takes place, perhaps deriving some nourishment from the female, but without the strong umbilical attachment to a placenta as in mammals; the true condition of so-called 'live-bearing' fishes - see also viviparous and oviparous

• P - R

• pectoral fin - pectoral, pertaining to the breast so referring to the position of the pectoral fin.
  
• pelagic - living and feeding in the open sea; associated with the surface or middle depths of a body of water; free swimming in the seas, oceans or open waters; not in association with the bottom. Many pelagic fish feed on plankton. Referring to surface or mid water from 0-200m depth
• pelvic fin See: Fins
  
• resting - see Fish Behaviour

• S

  • scales - most fish have scales. In sharks the scales are called dermal denticles. They are tiny tooth-like structures in the skin. They give the shark's skin a smooth appearance that feels like sandpaper. Bony fish scales are made of bone and look like the shingles on a roof
    
  • schooling - see Fish Behaviour

  • Senses -

    fish have a number of senses that help them survive in their environments. Humans share some of them, but others are found only in fish.

    sight: Most fish have well developed eyes which are located on the side of the head. This positioning allows the fish to see in every direction. Fish that are colourful probably have colour vision. Nocturnal fish have large eyes that help them see in the low light.

    smell and taste: Fish can smell things in the water with two blind sacs called nares. Nares are similar to our nostrils, except fish cannot breathe through their nares. A fish can taste with taste buds in the lining of its mouth and gills. Some fish have feelers, like the 'whiskers' on a catfish, called barbels, which are covered with taste buds.

    hearing: Fish have ears but you cannot see them. Their inner ears are well developed and pick up sound waves in the water through the fish's body.

    lateral line: The lateral line system helps the fish feel movements in the water. The line, actually a row of tiny holes in the skin, begins behind the gill cover and runs along the side of the body to the tail. Tiny hairs in the lateral line system are sensitive to vibrations. This system helps fish swim in schools, avoid predators and find food.

    electricity: Some bony fish and sharks have special pores on the head that allow them to detect electrical currents. This sense aids them in navigating or finding prey in dark or muddy water.

    Also See: Fish Senses

  • sight - see Fish Senses
  • smell - see Fish Senses

T - V

• tails - the shape of the tail can be an indicator of how fast a fish usually swims. Tails could be Crescent-shaped, Forked and Rounded shape. See: Fish Tails
• taste - see Fish Senses
• traumatogenic - causing an injury; eg, sharks that have been reported to attack humans.
• viviparous - giving birth or bringing forth living (active, free-swimming) young, rather than laying eggs; producing live young from within the body of the parent female - see also oviparous and ovoviviparous