126 MARKETABLE BRITISH MARINE FISHES 



long rough dab. Common star-fishes are occasionall)'- swallowed 

 by the haddock and long rough dab but, as might be expected, 

 the strong-spined sea-urchins do not serve as food for fishes 

 to any great extent ; some of the softer-shelled forms with 

 weaker spines {Spatani^iis, AiupJiidotus) arc however occasion- 

 ally eaten. 



But there are fishes which feed neither on the ground animals 

 nor on other fishes, namely, those which feed on the lower animals 

 that swim in the water. In other words, the water has a popu- 

 lation of lower animals as well as the ground under the water, 

 and this population supports different kinds of fishes. The swim- 

 ming animals now to be considered are all small, very small, or 

 extremely minute, but they make up by their numbers for their 

 small size, and consequently the amount of substance contained 

 suspended in the water of the sea is enormous, and forms a 

 very large supply of available food. This floating population of 

 the water consists partly of permanent elements, partly of 

 temporary, that is to say, partly of animals which live their 

 whole lives in this condition, partly of the minute young (larvae) 

 of nearly all the animals that in their adult condition live on the 

 bottom. The chief class among the permanent inhabitants is 

 that of the copepods, a particular division of the crustaceans, 

 ranging in size from \ inch downwards. These animals are 

 constantly and everywhere abundant, and their bodies are rich 

 in oil and extremely nutritious. With these there are swarms 

 of the larvae of larger crustaceans, worms, molluscs, and echino- 

 derms, which succeed one another according to the breeding 

 seasons of their parents, and are most abundant in summer. All 

 these together form the food of the teeming shoals of surface 

 or mid-water fish, namely, the herring, pilchard, and sprat. 

 The mackerel feeds by preference on young sprats or other 

 young fish which swim near the surface, but appears to 

 depend on the same kind of food as the herring at certain 

 times. 



Some examples of the numerous different minute forms 

 which live suspended in the water of the sea are represented in 

 Figs. 76-81. The copepod, shown in Fig. '/6, is one of the 

 largest and most abundant in the North Sea and on other parts 

 of our coasts. Fig. 80 represents a stage in the development of 

 a common swimming crab {Portiiiius). The actual length of a 



