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Biogeography

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Phylogeny and biogeography of liverbearers (genus Brachyrhaphis; figure credit: Ingley et al. 2015).

Biogeography is the study of patterns in distribution of fish (or other) species.  Biogeography provides an understanding of where populations are currently present and can help infer evolutionary relationships at a broad scale, including historic population isolation and colonization events.  Geologically, many species patterns can be tracked with plate tectonics.  The study of biogeography can also complement understanding of current ecological processes to explain distribution of populations at a local scale.

Please see here for more information.

BRD

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A shrimp net with a mesh-panel, bycatch reduction device (BRD) and grill-type, turtle excluder device (TED; photo credit: NOAA).

BRD is an acronym for bycatch reduction device.  Bycatch is non-target catch within any fishery.

For certain fisheries, these modifications to the gear (i.e., BRDs) can help lower the amount of bycatch.  For example, a turtle excluder device (TED) is a specific type of BRD designed to help turtles escape trawl nets.  Especially in cases where fisheries have bycatch quotas, the use of BRDs can often allow fisheries to operate longer, and more profitably, because the quotas are not exceeded quickly.

BRDs are generally designed with the cooperation of the fishery – they can be continually modified and improved to help ensure their effectiveness without compromising the productivity of the fishery – which is in the best interests of the industry and conservation, alike.

Bioluminescence

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Splitfin Flashlightfish are thought to produce the brightest glow of any living organism – they can be seen from over 100 feet away!

Splitfin Flashlightfish are thought to produce the brightest glow of any living organism – they can be seen from over 100 feet away!

Bioluminescence is a chemical process by which some fish species can produce their own source of light.  They have light producing organs known as photophores.  The light is emitted from specialized cells called photocytes or from symbiotic fluorescent bacteria that are cultured by the fish in photophores.  Most fish bioluminescence is blue (because blue-green light transmits furthest in water); this helps camouflage fish in open water because their counterillumination matches the ambient ocean color from above.  Other fish use different colors of bioluminescence, such as red or green or white, to reveal fish hidden by counterillumination, distract or confuse fish with bright flashes, or to signal to other fish (e.g., potential mates or members of their school).

For examples of bioluminescent fish, check out the “twinkle twinkle little fish” post on the Fisheries Blog!

Bioluminescent fish don't need twinkle lights to make their season bright!  Happy Holidays! (riverbanks.org)

Bioluminescent fish don’t need twinkle lights to make their season bright!  Happy Holidays! (riverbanks.org)

 

 

Bycatch

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Shrimp fisheries have historically had very high bycatch

Bycatch is non-target catch within any fishery.  Bycatch can be either different species from the target of the fishery or individuals from the target species, generally juveniles, which are not of a marketable size.  Most bycatch is tossed back because it is illegal to possess or it has no commercial value.  In certain fisheries, however, a certain amount of marketable bycatch can be kept to sell.  Including bycatch reduction devices (BRDs) that have been specifically developed for some fisheries can have significant impacts on the amount of bycatch and/or bycatch survival.  In cases where fisheries have bycatch quotas, the use of BRDs, such as Turtle Excluder Devices (TEDs), can often allow fisheries to operate longer because the quotas are not exceeded quickly.

Because bycatch is difficult to quantify, it makes it very difficult to assess the population status of bycaught species.  Overfishing for these species is sometimes not recognized until the population is severely overfished.  Including bycatch in stock assessment techniques is helping to improve sustainability of these species.

Benthic zone

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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!

Tripod fish use the benthic zone to feed

Tripod fish use the benthic zone to feed