Marine Aquaculture: Raising Salt Water Fish in Your ..

Our hypothesis of an osmotic limit for fishes is based on the extrapolated value for isosmotic state at 8,200–8,400 m, coinciding with the observed depth distributions of fishes. If this hypothesis is correct, what would prevent fish from evolving mechanisms to pass this barrier? To understand this, we must examine the evolutionary history of bony fishes. There is very strong phylogenetic, fossil, and physiological evidence that the ancestors of bony fishes evolved in fresh water (), which can approach 0 mOsmol/kg. Freshwater fish are therefore hyperosmotic at about 300 mOsmol/kg internally. To cope with this osmotic imbalance, these fish have (among other adaptations) kidneys with glomeruli, filtering structures that remove excess water from vertebrate bodies (). In evolving for seawater, shallow teleosts have become hypoosmotic at about 350 mOsmol/kg internally, with the opposite physiological processes, including inactive glomeruli or, in some groups, complete absence of glomeruli. These so-called aglomerular species include some gelatinous deep-sea fishes (). Many marine fish lineages have never returned to fresh water, including the Liparidae (no species of which have been found in low-salinity waters) (). Those that can reacquire hyperosmotic regulation during their life cycles, including euryhaline fish such as salmon, pause at an intermediate estuarine salinity as their gills reorganize and glomerular filtration is reactivated. This “reprogramming” of osmoregulation takes many hours or days ().

goby fish saltwater | Saltwater aquarium fish photos - Marine tropicals - Pinellas Aquariums

Marine and freshwater fish oil vary in contents of , EPA and DHA. The various species range from lean to fatty and their oil content in the tissues has been shown to vary from 0.7% to 15.5%. They also differ in their effects on organ lipids. Studies have revealed that there is no relation between total fish intake or estimated omega−3 fatty acid intake from all fish, and serum omega−3 fatty acid concentrations. Only fatty fish intake, particularly salmonid, and estimated EPA + DHA intake from fatty fish has been observed to be significantly associated with increase in serum EPA + DHA.

Marine fish spend their entire life in salt water

, a ,  bacteria caused losses in farmed marine and freshwater finfish of US$100 million in 1997. In contrast, whereas mudskippers (Periophthalmus sp., Family Gobiidae or “gobies”) rely on a combination of lateral undulations and pectoral fin locomotion underwater , they perform at least two distinct types of locomotion on land: crutching and jumping , . Crutching involves using the pectoral fins and tail as a tripod, providing stabilization while planting the pectoral fins to lift the body off the ground to move forward . While crutching tends to be slow, jumping is employed as a rapid, terrestrial escape response, remarkably similar to the terrestrial kinematics observed among the aquatic blennies studied here. When jumping, mudskippers simultaneously bring their head and tail together before rapidly extending the body to propel the fish away from a threat . Timing characteristics of water versus terrestrial escapes indicate that the maneuvers performed underwater may be Mauthner-mediated, whereas those on land are not – suggesting the use of a novel motor pathway for land-based escape behaviors .

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Some marine aquariums also include a . Refugiums are small containers or aquariums that are hidden behind or beneath the main aquarium and connected to it via a water pump (often in a similar manner to a sump). Refugiums have recently become quite popular among reef aquarists because they can be used to serve several purposes such as adding water volume or providing a fish-free site for biological filtration in live rock and/or the sandbed. Fish-free refugiums host populations of , , , and other .

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