The caudal fin, or tail, of a fish is the only fin to be connected to the vertebral column. It is the primary means of locomotion for most fish. Unlike many marine mammals with tails that use an up-and-down motion, fish generally use a side-to-side thrust of their caudal fin for propulsion. The shape of the caudal fin can be indicative of the style of motion for a fish. For example, very fast swimming fish like tunas have lunate caudal fins for more efficient swimming while lie-in-wait predators like grouper have a strong, wide base of the tail, the caudal peduncle, for faster acceleration.
The adipose fin is a small fleshy fin found posterior to the dorsal fin and anterior of the caudal fin. It is only found on few fish, including trout, salmon, and catfish. When it was named, it was thought to hold fat, or adipose, tissue. Once this hypothesis was disproved, fisheries biologists long considered this fin to be “non-functional.” More recently, research suggests that the adipose fin may serve as a “precaudal flow sensor” to improve maneuverability in turbulent waters. This new research may raise concerns because adipose fin clipping is commonly used to “tag” hatchery reared salmon to distinguish them from wild salmon for catch and release management purposes.
For more information on the adipose fin, please visit: http://thefisheriesblog.com/2013/05/28/the-adipose-fin-old-mysteries-with-new-answers/
The pelagic zone is the region of a body of water (lake, river, or ocean) that is not associated with the bottom (see benthic zone) or shore (see littoral zone). This habitat zone is truly a three dimensional habitat space. Some fish that occupy the pelagic zone never encounter the bottom or shore throughout their lives. Because the pelagic zone is a nutrient poor environment, large fish have two basic strategies to get meals – either swim long distances in search of nutrient-rich prey (like many oceanic sharks and tunas) or drift with currents and eat nutrient-poor prey (like the Ocean Sunfish Mola mola). The pelagic zone is divided into zones based on light penetration from the surface:
- Epipelagic (sunlight; 0-200m)
- Mesopelagic (twilight; 200-1,000m)
- Bathypelagic (no light; 1,000-4,000m)
- Abyssopelagic (4,000m – ocean floor)
- Hadopelagic (deep sea trenches)
The benthic zone is region of a body of water (lake, river, or ocean) that is near the bottom. It includes the surface and some of the sub-surface layers of the sediment. The sediment can sand, mud, rocks, coral, among other substances. Benthos are organisms living in the benthic zone. These organisms are predominately invertebrates, but the benthic community is very important to some fish species. For example, the tripod fish (Bathypterois grallator) is a deep-sea benthic fish that uses modified fins and fin rays to stand on the ocean floor and wait for prey items to approach. These fish can grow up to 3 feet long!
The littoral zone is the region of a body of water (lake, river, or ocean) that is near the shore. While there is no exact definition of the zone, in marine systems it is generally considered to extend from the high-water mark to the continental shelf; freshwater systems it is generally considered to be wetland zones where sunlight can still reach rooted plants. Because of its close association with terrestrial systems, the littoral zone is nutrient rich and highly productive. Fish in these areas, like coral reef fishes, for example, often become highly specialized feeders because of the diverse and abundant food sources.
IUU fishing is illegal, unregulated, and unreported fishing. According to the 2001 FAO International Plan of Action to Prevent, Deter and Eliminate Illegal, Unreported, and Unregulated Fishing,
Illegal fishing refers to activities:
- conducted by national or foreign vessels in waters under the jurisdiction of a State, without the permission of that State, or in contravention of its laws and regulations;
- conducted by vessels flying the flag of States that are parties to a relevant regional fisheries management organization but operate in contravention of the conservation and management measures adopted by that organization and by which the States are bound, or relevant provisions of the applicable international law; or
- in violation of national laws or international obligations, including those undertaken by cooperating States to a relevant regional fisheries management organization.
Unreported fishing refers to fishing activities:
- that have not been reported, or have been misreported, to the relevant national authority, in contravention of national laws and regulations; or
- undertaken in the area of competence of a relevant regional fisheries management organization which have not been reported or have been misreported, in contravention of the reporting procedures of that organization.
Unregulated fishing refers to fishing activities:
- in the area of application of a relevant regional fisheries management organization that are conducted by vessels without nationality, or by those flying the flag of a State not party to that organization, or by a fishing entity, in a manner that is not consistent with or contravenes the conservation and management measures of that organization; or
- in areas or for fish stocks in relation to which there are no applicable conservation or management measures and where such fishing activities are conducted in a manner inconsistent with State responsibilities for the conservation of living marine resources under international law.
While all three types of IUU fishing result from a lack of resources (to enforce, report, and regulate), lumping these three different types of fishing under one category simplifies the complex issues, linking illegal activities (i.e., illegal fishing) with legal activities (i.e., unreported and unregulated fishing). Illegal fishing is a regulatory issue; unreported and unregulated fisheries do not break any law – they are management issues, or rather a lack of management issue. IUU fishing often basks in a negative light, but this legal distinction makes it difficult to chastise fishermen just because their government lacks the capabilities to report or regulate their fishery. For more information on the challenges to managing IUU fishing, please refer to the following AFS publication:
Serdy, Andrew. 2011. Simplistic or Surreptitious? Beyond the Flawed Concept(s) of IUU Fishing. Pages 253-279 in W.W. Taylor, A.J. Lynch, and M.G. Schechter, editors. Sustainable Fisheries: Multi-Level Approaches to a Global Problem. American Fisheries Society, Bethesda, Maryland.
Ichthyology is the study of fishes*. With an estimated 27,977 species, fish are the most numerous and diverse group of vertebrate species. In fact, there are more fish species than all other groups of vertebrates (amphibians, reptiles, birds, and mammals) combined.
One could argue that people have been studying fish for the purposes of food since prehistoric times, but the scientific study of fish began in earnest during the European Renaissance. While famed taxonomist Carolus Linnaeus did identify many fish species, his colleague, Peter Artedi, is considered the “father of ichthyology” for standardizing morphometric (measurement ) and meristic (count) methods still used to classify species. According to FishBase, a comprehensive, publically accessible database of fish species , over 10 species are named in his honor.
Beginning with basic anatomy and systematics (study of evolutionary relationships among fishes), ichthyology has broadened to include ecology (study of interactions between fish and their environment), physiology (study of internal function of fish), and behavior. Ichthyology forms the foundation of fisheries science which applies the understanding of fishes in the context of fisheries (the harvest of fish and other aquatic organisms for human use).
*Note that fish is singular and plural when in reference to a single species. Fishes is plural in reference to more than one species.
Polyandry is a polygamous mating system where a female has multiple male partners during the breeding season. This is a relatively uncommon form of polygamy and has only been reported in anemonefish (Amphiprioninae) and could be the case for deep sea anglerfish (Ceratiidae). Though anemonefish are generally monogamous, polyandry has been reported in some circumstances. In Deep Sea Anglerfish, multiple males can be attached to a large female, almost in a parasitic relationship where their circulatory system merges with the female’s. See polygamous; polygyny.
Polygamous is a mating system in which an individual of one sex has multiple partners during the breeding system but individuals of the opposite sex have only one partner. Evolutionarily, these systems are purported to have an increased chance of passing on “good genes” from individuals that compete for the ability to mate with multiple partners. This mating system can occur with one male and many females (see polygyny) or one female and multiple males (see polyandry).
Promiscuous is a mating system where both sexes have multiple partners during the breeding system. In fishes, this is the most common mating system. Breeders make
little or no mate choice and spawn with multiple partners, either sequentially or at the same time.
Breeding aggregations of promiscuous spawners can make some fish species particularly vulnerable to fishing. The fish generally assemble according to environmental cues (e.g., temperature, moon phase) that are known to fishermen. Overfishing on spawning aggregations can be particularly devastating to fish populations because the high fecundity (fertility) individuals are readily removed from the population. The Nassau grouper (Epinephelus
striatus), for example, once supported an important Caribbean fishery but is currently endangered because of overfishing on these spawning aggregations.