SEA-FISHERIES LABORATORY. 279 



them with certainty. They were observed in the central 

 area nearly a fortnight earlier than in Port Erin Bay in 

 1914. The eggs were found for the first time in the Bay 

 plankton on March 4th, and were of frequent occurrence 

 both inside the Bay and at the observation stations 

 outside during March, April and May. As usual, the 

 largest numbers were taken at the open sea stations. It 

 was estimated that 2,660 bib or poor cod eggs, probably 

 both species, were present in a haul taken at Station III 

 on April 3rd. 



The maximum spawning period of the valuable 

 gadoids frequenting the area at the South-West of the 

 Isle of Man in 1914 appears to have been at the 

 beginning of April. The largest numbers of eggs were 

 found on April 3rd and 4th. 



Onos spp., Risso. — The Rocklings. 



The eggs of one or more species of rockling are 

 amongst the first of the pelagic fish eggs to make their 

 appearance in the plankton of the Irish Sea, and are 

 usually the last to disappear. Their occurrence in the 

 Bay in 1914 extended from January 19th right on through 

 the spring, summer and autumn until October 9th. This is 

 almost identical with the distribution found in 1910. There 

 is a distinct variation to be found amongst the eggs, both 

 in the size of the egg itself and of the oil-globule. It is 

 almost certain that two species of rocklings are occasion- 

 ally represented in the same haul. Rockling eggs 

 collected in September measured 0832 mm. in diameter 

 with an oil-globule 0176 mm., and 067 mm. in diameter 

 with an oil-globule 015 mm. 



Scomber scomber, Linn. — Mackerel. 

 Eggs identified as those of the mackerel only 

 occurred twice during 1914. Two were found in Port 



