Fish on Friday II: Monastic Meals
http://www.medievalists.net/2017/04/fish-on-friday-monastic-meals/
Medieval Food Archive
http://www.medievalists.net/tag/medieval-food/
Disrupting spawning beds
Salmon largely disappeared from our waters due to the construction of water mills, ecologists [from university in Netherlands] conclude. The construction of water mills caused the destruction of the gravel beds in streams, making them unsuitable for salmon to spawn. Whereas it was previously thought that water contamination was the most likely explanation, archival research demonstrates that salmon stocks had already dwindled prior to the invention of the steam engine.
https://www.sciencedaily.com/releases/2016/07/160720094432.htm
It would be very hard to say at some point in time, that all fish have spawned.
Spawning time might vary from season to season due to variations in natural environment and in healthy populations it stretches over considerable amount of time (you could look on this as some sort of natures safety element).
It is best to take a walk now and then by your stream and you will notice spawning holes (reeds) on the ground. It was described in literature that brown trouts actually start digging them weeks before actual spawning. But that would be a reliable method to determine spawning time in your river/stream.
Brown trouts will attack lures through the whole winter so i doubt that there would be any serious non-feeding time after spawning. Although it is closed season, we do catch them while hucho fishing. In fact I have the feeling they are even more aggressive at that time.
In previous years, up to and including 2009, I've observed trout migrating from the main river (Wye) in September and October, as we would expect.
Yes they have stopped spawning. Brownies spawn on day length, hence why they spawn in December.
Quite right - rainbows and salmon too! Some fish farmers trick the fish into spawning early or late by keeping them in controlled light environments. By keeping the day length longer during the autumn you can delay spawning time until after 'normal' fish have spawned. That way you can produce more eggs and fry and not have all the tank space used up at the same time.
We used to select broodstock from the very earliest fish to spawn and the very latest fish to spawn and by doing it year after year we increased the spawning period by several weeks at each end of the season. This was another way of producing more fry from the same number of available tanks.
http://www.flyforums.co.uk/trout-grayling-fishing/65806-spawning.html
Trout Production: Handling Eggs and Fry
Trout eggs are usually shipped when they reach the “eyed” stage, which is more than halfway through the incubation period.
Incubation time is temperature dependent. At 55 °F, rainbow trout eggs will hatch approximately 3 weeks after fertilization, or within 4 to 7 days after being received as “eyed” eggs. At 45 °F, the eggs will hatch approximately 7 weeks after fertilization.
Egg incubation
All types of egg incubators should be covered to protect developing embryos from direct light. However, if the eggs are more than 3 days from hatching, dead eggs should be removed regularly to limit fungal infections. Removing dead eggs is more effective than chemical treatment at controlling fungus, but can be very time consuming.
Handling sac fry
Hatching rate depends on water temperature, but usually will be completed within 2 to 4 days after commencing. Empty shells should not be allowed to accumulate in the incubating units. If the eggs are incubated separately from the rearing troughs, the sac fry should be transferred into troughs shortly after hatching is complete. Up to 30,000 fry can be stocked into a standard fry trough 10 feet long and 18 inches wide. The water flow rate should be 8 to 10 gallons per minute for most facilities. Keep the water level in the trough fairly shallow (3 to 4 inches) and the flow reduced until fry “swim up,” approximately 2 weeks after hatching at 55 oF. Any dead fry, egg shells or deformed fish should be removed regularly.
When about 50 percent of fry “swim up,” begin feeding with a small amount of starter mash on the surface three to four times daily. Continue until most fish are actively feeding. Feed every 15 minutes if possible, but not less than hourly at this stage. A large kitchen strainer makes an excellent tool for distributing the starter feeds throughout the tank. Automatic feeders are certainly more convenient than feeding by hand, but many are not well suited to distributing the smallest feed sizes.
Feed approximately 10 percent of the fish weight per day for 2 to 3 weeks, or until fry are about 1 inch long (approximately 1,000 per pound); then feed according to a published feeding chart. Fry feed should be formulated to contain approximately 50 percent protein and 12 to 15 percent fat. Excess feed and fish waste must be removed from the troughs at least daily. Small paintbrushes or feathers work well for cleaning the rearing troughs.
Siphons also can be used if care is taken to avoid the fish. After the fry have been actively feeding for 2 weeks, sample count the fish every week and adjust the feeding rate and feed size accordingly. Adjust the fish densities in the troughs as necessary to prevent overcrowding. In the standard fry tank described previously, fish are typically kept below 1 pound of fish per cubic foot of water volume. Monitoring dissolved oxygen levels will help determine when fry density should be reduced. Ideally, the dissolved oxygen level should not be lower than 6 ppm. The fry will be ready to move into larger tanks in the hatchery when they grow to 1 inch in length. In areas where Yersinia ruckeri, the causative agent of enteric redmouth disease (ERM), has been detected, the fish should be vaccinated 2 weeks before moving them to a production facility. The recommended minimum size for immersion vaccination of trout against ERM is 4.5 grams, or approximately 100 fish per pound.
http://www.arkive.org/brown-trout/salmo-trutta-fario/video-fa09b.html
Breeding
All trout return to the rivers and streams to spawn. Timing will depend on latitude (day length), but here on the Tay it takes place in November/December. The trout seek out gravel beds (stones about the size of a pea are best) with good water flows over it to bring in oxygen and to carry away silt. The hen fish cuts a trench (redd) into the gravel with her tail fin. Once dug she is joined in the hole by the male. Hundreds of eggs and milt are squirted into the base of the redd simultaneously. Thus fertilised the eggs absorb water and sink. They are quickly covered up by the female. Inevitably eggs miss the redd and drift downstream. Fish including other trout will eat them, but some will find their way into other cracks and crevices where they may well develop.
http://www.fishingnet.com/brown_trout.htm
Brown trout Salmo trutta fario
Size Length: up to 50 cm (2)
Weight up to 2 kg (2)
For more information on the brown trout, visit:
• BBC Wildlife Finder:
http://www.bbc.co.uk/nature/species/Brown_trout
• Fishbase species account, available at:
http://www.fishbase.org
Inhabits well-oxygenated streams and rivers (4).
This fish feeds on invertebrates, insect larvae, aerial insects, and molluscs, as well as the occasional fish and frog (3). Spawning occurs between January and March, when females are accompanied by a number of males. The eggs, which are fertilised externally, are covered with gravel by the female. For the first days after hatching, the young fish (fry) derive their nutrients from their large yolk sacs; they then feed on small arthropods, such as insect larvae (2). The maximum-recorded life span of a brown trout is 5 years (3).
The brown trout is found throughout Europe; those that live in rivers which empty into the North Sea and the Baltic Sea belong to the subspecies Salmo trutta fario, those that live in rivers that empty into the Black Sea are of the subspecies Salmo trutta labrax, and those in rivers emptying into the Mediterranean belong to the subspecies S. t. macrostigma (2). The brown trout (Salmo trutta fario) is found throughout the British Isles (4).
The brown trout is a beautiful fish, similar in general shape to the salmon; the back is dark, the sides pale, and both are flecked with variable reddish spots that have pale borders (4). The belly is a creamy yellowish-white. Juveniles and immature adults can be distinguished as they have bluish-grey spots, and adult males have a strongly curved lower jaw (2).
Larvae: stage in an animal's lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.
http://www.bbc.co.uk/nature/species/Brown_trout
References
1. National Biodiversity Network Species Dictionary (Jan 2003):http://www.nhm.ac.uk/nbn/
2. Cihar, J. (1991)A field guide in colour to freshwater fish. Silverdale Books, Leicester.
3. Fishbase species account (Jan 2003):http://www.fishbase.org/Summary/SpeciesSummary.cfm?genusname=Salmo&speciesname=trutta%20fario
4. Buczacki, S. (2002) Fauna Britannica. Hamlyn, London.
http://www.arkive.org/
http://www.arkive.org/brown-trout/salmo-trutta-fario/video-fa02.html#text=All
About
The brown trout (Salmo trutta morpha fario and S. trutta morpha lacustris) and the sea trout (S. trutta morpha trutta) are fish of the same species.
They are distinguished chiefly by the fact that the brown trout is largely a freshwater fish, while the sea trout shows anadromous reproduction, migrating to the oceans for much of its life and returning to freshwater only to spawn. Sea trout in the UK and Ireland have many regional names including sewin (Wales), finnock (Scotland), peal (West Country), mort (North West England) and white trout (Ireland).
The specific epithet trutta derives from the Latin trutta, meaning, literally, "trout".
The lacustrine morph of brown trout is most usually potamodromous, migrating from lakes into rivers or streams to spawn, although there is some evidence of stocks that spawn on wind-swept shorelines of lakes. S. trutta morpha fario form stream-resident populations, typically in alpine streams but sometimes in larger rivers. There is evidence that anadromous and non-anadromous morphs coexisting in the same river can be genetically identical. In common usage, the name "brown trout" is often applied indiscriminately to the various morphs.
Semelparous organisms reproduce only once in their lives and then die. The most well known ones are Pacific salmon that perish after spawning. Other examples are squid, mayflies and plants which die after setting seed (annuals). The adult diverts resources into producing huge amounts of offspring to ensure sufficient numbers reach maturity without any parental care. This is why bears largely ignore dead salmon after they've spawned - all the salmon's fat has gone into producing sperm and eggs and little nutrional value is left.
Distilling wine
https://youtu.be/G1IUm3V546k?t=46m58s
