Coal Barges £120 on the time
Coal load value £6
Skates are long-lived animals. They take 5-10 years to mature and lay relatively few eggs (about 40 - 150 a year), making them particularly vulnerable to overfishing, whether by trawls, longlines or set nets. Large juveniles are often caught before they have started breeding and most species can’t rapidly replace the animals that are removed by fisheries. Smaller species tend to grow and breed more rapidly, however they are of lower commercial value than large-bodied species.
For these same reasons, skates and rays do not tend to support large commercial fisheries, which mean they have received far less attention from researchers and fisheries managers than the more economically-important bony fish species. These factors make the largest skates and rays among the most threatened species in British waters. For example, the Common Skate (now recognised as two distinct species: Blue Skate and Flapper Skate), the biggest and formerly one of the more abundant species around the British Isles, is now absent from much of its former range. Conversely, populations of some of the smallest species, such as the Cuckoo Rays and Spotted Rays, remain healthy.
Metabolic relationship of London with the estuary