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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.

FAD (Fish Aggregating Device)

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Sophisticated fish aggregating devices can include their own moorings

Sophisticated fish aggregating devices can include their own moorings

Fish Aggregating Devices (FADs) are man-made objects that are used to attract fish and facilitate their capture.  FADs can range from crude wooden rafts tied to navigational buoys to sophisticated anchored systems.

These devices are very effective at attracting fish that favor submerged objects.  Prey fish use them for shelter and predatory fish follow the prey fish.  As a result, whole fish communities can develop around them and make them reliable fishing grounds.  Pelagic fish, such as tunas, billfish, dolphin fish, sardines, and sharks, have all been known to frequent FADs.  While they are predominately used to increase fishing productivity, FADs have also been used to support research on fish behavior and used within fisheries management strategies.

A crude wooden raft can still serve to attract fish

A crude wooden raft can still serve to attract fish

 

Finlets

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Finlets may reduce turbulence for high-efficiency swimmers

Finlets may reduce turbulence for high-efficiency swimmers

Finlets are highly specialized fins located on the dorsal and ventral sides of the body between the dorsal fin and/or the anal fin and the caudal fin.  They are only found on certain fish including those in the Scombrid family (mackerels, tunas, and bonitos), Scomberesocid family (sauries), snake mackerels (family Gempylidae), and Bichirs (family Polypteridae).  For Bichirs, the finlets are only on the dorsal side and they take the place of a traditional dorsal fin.  For Scombrids and Scomberesocids, finlets are small, rayless, non-retractable fins located on both the dorsal and ventral margins of the body.  Finlets in Scombrids have been evaluated for their contribution to locomotion because these fish are such high-performance swimmers.  Finlets may contribute to dampening of cross-flow turbulence around the caudal peduncle.

Finlets are found behind dorsal and anal fins

Finlets are found behind dorsal and anal fins