a. 

 b. 



d. 



F-30 



SounH scientific i n f o rm-i.t i on on the pbate of krill stocks. 



Advice on the effect of exploitation on the stocks of krill and 

 its consumers ajid prediction of anticipated changes as a result 

 of different fishing strategies. 



International agreement on management plans resulting from a and b. 



Implementation of management plans. 



Tlie known reliance by most of the whales, seals and birds indicated in section 6.7 plus 

 the probable reliance of a sigiificant proportion of the fish and squid stocks on krill 

 indicates that, as far as management decisions are concerned, krill cannot be considered in 

 isolation. These interactions are discussed later in Chapter 10 in which the conclusions 

 based on an assessment of each single resource are brouf^t together. The ronainder of this 

 section will be concerned with stock assessment as related solely to krill. 



A convenient, and often used, estimate for the maximum size to which a fishery should 

 be permitted to develop is the maximum sustainable yield (MSY). This may be defined as the 

 greatest constant amount of the resource that can bo extracted annually (and therefore by 

 implication be replaced at the same annual rate) in the long tenn. This does not mean that 

 an aim of management is to achieve this level of exploitation, but rather to define an upper 

 limit beyond which a long terra fishery should not develop. In the case of krill because of 

 the wide range of consumers in addition to man that are utilizing krill the fishery could 

 not develop to the theoretical HSY without causing considerable imbalance in the ecosystem. 



As a first approximation a "SCIIAEPER" type model can probably be used. This requires 

 information in two of three forms: catch, effort and biomass. Of these three the catch is 

 the simplest to determine. Estimation of fishing effort presents several problems in decid- 

 ing on a realistic index. Tlie present trend in the fishery suggests that any major expansion 

 will be as a pelagic trawl fishery. The fishing effort may be divided into a series of 

 components each of different relative importance (Table 6.15). 



Table 6.15. Major components of fishing effort in a trawl fishery for 

 krill with their relative importance. 



Fishing Effort Component 



Relative Importance 



1. Gear 



a) Size of net 



b) Gear saturation 

 (includes saturation 

 of handling capacity) 



Moderate importance, depends on engine power. 



Likely problem since present evidence suggests 

 catching capability may exceed processing 

 capacity. 



?. VesrsGl 



a) oize 



b) Power 



lov importance. Only relatively large vessels 

 may be able to operate in Southern Ocean. 



Moderate importance since teclinique is 

 essentially aimed trawling. 



