nmonks
A stroke of the brush does not guarantee art from
Bignose,
Within the handful of generations fish have been bred on farms, it is unlikely they have "evolved" to deal with salty water any better. It's just too short a period of time. Evolution of fish likely needs hundreds, if not thousands, of generations. So I don't think the addition of salt is a "new" feature unique to farm-bred fish compared with their wild-caught ancestors.
That said, fish can and do become acclimated to water conditions, just as we do to local conditions. Some who lives in Texas might find the UK rather cold for the first few weeks, but eventually they'd adapt and not notice it. If they had a child, that child would be used to UK temperatures, and going back to Texas might find it rather hot, as would their parents, at least for a few weeks until they all got used to it. So in this case it's experience rather than genes that set the standard of what conditions are "normal". Thus, wild caught fish should be amenable to exactly the same conditions as tank-bred ones, they might simply need to be acclimated to them more gradually.
The whole primary/secondary freshwater fish issue is much more complex than some people appreciate. For a start, these terms properly apply only to families of fish, not smaller groups (e.g., species) or bigger ones (e.g., order). The Cichlidae are secondary freshwater fish, but the Siluriformes are not. Within the Siluriformes, there are primary freshwater fish families, like the Loricariidae, fully marine families, like the Ariidae, and groups that are arguably secondary freshwater fish, the Plotosidae, with some marine species but mostly freshwater ones evolved from marine species (in Australia).
Even within primary freshwater fish families there is a range of salt tolerances. I know of at least two species of Hypostomus that normally inhabit brackish, not freshwater, conditions plus the common Hypostomus plecostomus is widespread in brackish waters in Florida. Roach and dace, two cyprinids, are common in the low-end brackish parts of the River Thames, and some of the climbing perches and gouramis, families Anabantidae and Osphroneminae, are found in brackish water in the wild (e.g., Osphroneminae goramy, Anabas testudiens). Spiny eels are another group of primary freshwater fish including several brackish water species, and at least one tetra, the x-ray tetra, naturally occurs in slightly brackish water.
Conversely, there are species from secondary freshwater fish with a lower salt tolerance than these. Several of the soft water cichlids fall into this category (e.g. angels, rams) as well as the Rift Valley cichlids like mbuna that seem to get things like Malawi bloat when exposed to salt over the long term. Likewise the soft water killifish.
Dave Sands' quote is anecdotal, and I personally DO NOT recommend keeping Corydoras in brackish or even slightly salted water. The book doesn't discuss osmoregulation at all.
Really, all I wanted to raise was the fact that salt-tolerance is FAR more complex than many people realise. That's why I am fascinated by brackish water fish and brackish water environments.
Cheers,
Neale
Within the handful of generations fish have been bred on farms, it is unlikely they have "evolved" to deal with salty water any better. It's just too short a period of time. Evolution of fish likely needs hundreds, if not thousands, of generations. So I don't think the addition of salt is a "new" feature unique to farm-bred fish compared with their wild-caught ancestors.
That said, fish can and do become acclimated to water conditions, just as we do to local conditions. Some who lives in Texas might find the UK rather cold for the first few weeks, but eventually they'd adapt and not notice it. If they had a child, that child would be used to UK temperatures, and going back to Texas might find it rather hot, as would their parents, at least for a few weeks until they all got used to it. So in this case it's experience rather than genes that set the standard of what conditions are "normal". Thus, wild caught fish should be amenable to exactly the same conditions as tank-bred ones, they might simply need to be acclimated to them more gradually.
The whole primary/secondary freshwater fish issue is much more complex than some people appreciate. For a start, these terms properly apply only to families of fish, not smaller groups (e.g., species) or bigger ones (e.g., order). The Cichlidae are secondary freshwater fish, but the Siluriformes are not. Within the Siluriformes, there are primary freshwater fish families, like the Loricariidae, fully marine families, like the Ariidae, and groups that are arguably secondary freshwater fish, the Plotosidae, with some marine species but mostly freshwater ones evolved from marine species (in Australia).
Even within primary freshwater fish families there is a range of salt tolerances. I know of at least two species of Hypostomus that normally inhabit brackish, not freshwater, conditions plus the common Hypostomus plecostomus is widespread in brackish waters in Florida. Roach and dace, two cyprinids, are common in the low-end brackish parts of the River Thames, and some of the climbing perches and gouramis, families Anabantidae and Osphroneminae, are found in brackish water in the wild (e.g., Osphroneminae goramy, Anabas testudiens). Spiny eels are another group of primary freshwater fish including several brackish water species, and at least one tetra, the x-ray tetra, naturally occurs in slightly brackish water.
Conversely, there are species from secondary freshwater fish with a lower salt tolerance than these. Several of the soft water cichlids fall into this category (e.g. angels, rams) as well as the Rift Valley cichlids like mbuna that seem to get things like Malawi bloat when exposed to salt over the long term. Likewise the soft water killifish.
Dave Sands' quote is anecdotal, and I personally DO NOT recommend keeping Corydoras in brackish or even slightly salted water. The book doesn't discuss osmoregulation at all.
Really, all I wanted to raise was the fact that salt-tolerance is FAR more complex than many people realise. That's why I am fascinated by brackish water fish and brackish water environments.
Cheers,
Neale
