32 Fishery Board for Scotland. 



The Age of the Small Bottom Forms. 



A study of tlie developmental changes in small bottom forms has shown that, 

 when they first take to a bottom habitat, the chaiige from the pelagic form is not 

 yet complete. The transition is gradual, and the typical or perfect ground -form 

 is not attained until the fish has grown to a length of almost 180 jum. 



Fulton (1902) is the only investigator who has endeavoured to estimate the 

 age of the bottom forms. The task was a very difficult one, OAving to the absence 

 of complete information regarding the earliest bottom stages. 



It is perhaps best to deal, first of all, with the series from the Mediterranean, 

 where the sequence of appearance of the different stages seems quite intelligible 

 The Angler spawns in the Mediterranean in the winter months — eggs with ad- 

 vanced embryos were obtained by Lo Bianco in January and February. The young 

 pelagic forms were caught by Graeffe in the open sea of the Adriatic in the months 

 February, March, April. Post-larval stages (15-55 mm. in length) appear in the 

 Gulf of Trieste from September to February. Lo Bianco caught small bottom 

 forms 6-15 cms. long on shallow ground in the Mediterranean in the months March 

 to May. The small bottom forms caught in the months March to May, therefore, 

 belong to the brood of the previous year. 



The smallest bottom forms, caught in Scottish waters, are therefore comparable 

 with the smaller Mediterranean bottom forms just mentioned. They are' 64, 67, 

 69, 72, 83, 94, and 116 mm. long respectively, and were caught in the months 

 July, September, and October. It has been shown that they have not yet completed 

 their metamorphosis, although they have assumed a bottom habitat. These small 

 bottom forms, therefore, belong obviously to an earlier brood than the post-larval 

 forms which appear in the same areas at the same time, and, as the general spawning 

 period occurs in the locality in the months May, June, July, the small bottom 

 forms must be at least a year old. The results are, in fact, in close agreement 

 with those from the Mediterranean. 



Comparison may now be made with the series obtained by Fulton. His material 

 was very much restricted at its lower limits, as the smallest specimen obtained by 

 him was already 127 mm. long. The smallest series was, however, obtained off 

 Lybster, on the Caithness coast, in the month of November. The individuals 

 ranged from 127 mm. in length to 214 mm., and the mean size of the thirty-six 

 specimens was 161 '5 mm. Owing to the absence of information concerning the 

 later post-larval and very young bottom forms, Fulton underestimated the age 

 of this series ; they are undoubtedly at least one year and six months old. The 

 members of the other series are, therefore, correspondingly at least one year older 

 than is stated. It would probably be correct to say that the Angler is very rarely 

 caught in the North Sea by the commercial trawl before it has reached an age of 

 at least two years. 



Distribution op the Adult. " 



The known distribution of the young stages of Lo'phius jnscatorius has now been 

 very exhaustively treated, bu^t so far no reference has been made to the distribution 

 of adult forms. The adult has, however, a very wide distribution ; it is found 

 on both sides of the Atlantic. On the European side, it occurs as far north as 

 Iceland and the Faroes, and beyond 69° N. on the Norwegian coast, whilst, according 

 to Goode and Bean (1895), it extends as far south as the Cape of Good Hope. It 

 is met with frequently in the Baltic. All round the Scottish coast, it is caught in 

 considerable numbers. Fulton (1902) records the Angler as common both in the 

 inshore waters and in the greatest depths at which trawlers work, and states that 

 it seems to be most abundant in waters of moderate depth. 



It also occurs in the Mediterranean. Lo Bianco (1908-1909), in describing 

 the fauna of the Gulf of Naples, says that the adult is not rare, and attains some- 

 times the weight of 20 kilos. ; it is caught in numbers, principally during winter 

 and spring. According to Goode and Bean (1895), however, there is another species 

 of Lophius confined to the Mediterranean. This is Lophius hudegassa Spinola, 

 and it is distinguished from the other Lophiidse by its shorter second dorsal and its 

 simple lanceolate humeral spine. 



