~ 
~ 
might have enabled us, from a consideration of the 
relative increments in the catches from year to year, to 
have connected the increase on the Blackpool ground with 
its closure against the destruction of immature soles by 
shrimp trawling. But comparatively few hauls have been 
made on the Blackpool ground, and the opportunity has 
been lost. 
No regular observations regarding the distribution of 
the plankton or of the bottom invertebrate fauna of the 
Mersey ground have been made, and we have therefore no 
material for a possible explanation of the fluctuation in 
the fish fauna outlined above. It is particularly un- 
fortunate that regular and exact physical determinations 
of temperature, specific gravity, salinity, &c., were not 
made during the last eight years. These must be 
essential portions of any future investigation of this area.* 
The nature of the sea bottom is very peculiar, and a com- 
plete investigation of this is to be desired. 
We believe that observations on this ground, with a 
view to the regulation of the fishing, will be unsatis- 
factory unless accompanied by enquiries into the relations 
of its fish population with the spawning fish on the off- 
shore grounds on the one hand, and with the larger 
immature fish population of the offshore grounds on the 
other. Such investigation and enquiries into the stability 
of the immature fish population of the shrimping ground 
are very relevant. 
* See scheme given in this Report, p. 24. 
