July 1951 CQ^MSRCIAL FISHERIES REVJEaT 51 



WITHIN THE AREA I NVEST I GATED , I NCLUD I NG THE REGION NOW IN- 



TENSIVELY FISHED, PLANKTON WAS ABUNDANT AND DOMINANTLY PHYTOPLANK- 

 TONIC IN COMPOSITION INSHORE, BUT RELATIVELY POOR AND DOMINANTLY 

 ZOOPLANKTONIC IN COMPOSITION OFFSHORE. THE ANNUAL OCCURRENCE OF THE 

 PLANKTON I C STAGES OF NO LESS THAN 45 SPECIES, REPRESENTING ALMOST 

 ALL GROUPS OF THE ANIMAL KINGDOM, WAS ESTABLISHED FROM EXAMINATION 

 OF THE PLANKTON CATCHES. FROM A QUANTITATIVE POINT OF VIEW, IT IS 

 CLEAR THAT THE HUGE SHOALS OF MATURING PILCHARDS FREQUENTING ST, 

 HELENA BAY HAVE MORE THAN AN ADEQUATE FOOD SUPPLY IN THESE INSHORE 

 WATERS. IN REGARD TO THE PLANKTON I C DEVELOPMENT STAGES OF THE PIL- 

 CHARD IN THE PLANKTON CATCHES, IT APPEARED THAT PRESCALEO LARVAE AND 

 EGGS WERE COMPLETELY ABSENT IN INSHORE WATERS, WHERE CRUSTACEOUS AND 

 DIATOMACEOUS PLANKTON ORGANISMS WERE FOUND TO BE MOST ABUNDANT AND 

 SURFACE TEMPERATURES WERE LOWEST. IN OFFSHORE WATERS, WHERE THE SUP- 

 PORTING PLANKTON WAS CONSISTENTLY POOR IN QUANTITY, DISTINCTLY AN 

 OCEANIC TYPE IN WHICH SALPS, DOLIALIDS AND OTHER TUNICATES WERE FRE- 

 QUENTLY REPRESENTED, AND THE SURFACE TEMPERATURES WERE HIGHER THROUGH- 

 OUT, SUCH LARVAE AND EGGS NEVER OCCURRED IN LARGE NUMBERS. 



SPAWNING OR BREEDIN G AREAS ; IN REGARD TO PILCHARD SPAWNING OR BREEDING 

 AREAS, THE POSITION TO DATE IS THAT NEITHER A SPECIFIC SEASON NOR A 

 LOCUS OR LOCI HAVE BEEN FOUND. NO PATTERN OF OCCURRENCE A ND/OR DIS- 

 TRIBUTION IS DISCERNIBLE TO DATE AND THE NUMBERS OF PILCHARD EGGS AND 

 LARVAE FOUND WERE NEVER LARGE ENOUGH TO INDICATE MASS SPAWNING AT ANY 

 POINT OR OVER ANY AREA OF CONCENTRATION DURING ANY SPECIFIC PERIOD OF 

 TIME. THE COMPLETE ABSENCE OF EGGS AND LARVAL FORMS FROM INSHORE 

 WATERS, WHICH INCLUDE ST. HELENA BAY AREA, WAS INDICATIVE OF THE FACT 

 THAT BREEDING DOES NOT TAKE PLACE IN THE WATERS CURRENTLY FISHED COM- 

 MERCIALLY. ADULT FISH CAUGHT COMMERCIALLY IN THE ST. HELENA BAY AREA, 

 MORE ESPECIALLY THOSE CAUGHT CLOSE INSHORE, WERE GENERALLY SEXUALLY 

 INACTIVE. SUCH ACTIVITY WAS SLIGHTLY MORE MANIFEST IN FISH CAPTURED 

 IN THE SEAWARD PARTS OF ST. HELENA BAY, BUT ON NO OCCASION WAS A 

 SINGLE FISH FOUND IN A RIPE-RUNNING CONDITION. AN INDICATION TO THE 

 EXTENT OF THIS SEXUAL ACTIVITY WAS THE FACT THAT INSHORE-CAUGHT FISH 

 HAD BEEN FEEDING VORACIOUSLY, WHEREAS SEAWARD-CAUGHT FISH HAD BEEN 

 FEEDING LESS ACTIVELY. 



FEEDING ; ADULT FISH APPARENTLY SUBSIST ON A DIET ALMOST EXCLUSIVELY 

 PHYTOPLANKTONIC IN COMPOSITION, AND IN THIS REGARD THEY ARE SELECTIVE 

 FEEDERS IN RELATION TO THE AVAILABLE ZOOPLANKTONIC FOODSTUFFS. SE- 

 LECTIVE FEEDING WITHIN THE PHYTOPLANKTONIC FIELD HAS NOT YET BEEN 

 DETERMINED. PRESEALED LARVAL FORMS, ON THE CONTRARY, APPEAR TO FEED 

 PRACTICALLY EXCLUSIVELY ON ZOOPLANKTONIC ORGANISMS, BUT TO DATE, 

 THESE DATA ARE INCONCLUSIVE. 



AGE analysis : SCALE AND OTOLITH STUDIES SHOWED WITH REASONABLE SURETY 

 THAT THE COMMERCIALLY-EXPLOITED PILCHARD POPULATION IS GENERALLY COM- 

 POSED OF FISH BETWEEN 2 AND 4 YEARS OF AGE. SOME 5-YEAR-OLD FISH MAY 

 HAVE BEEN PRESENT IN SMALL NUMBERS, BUT FISH UNDER 2-YEARS OLD WERE 

 EITHER ABSENT FROM THE AREA, VERY RARE, OR NOT CAPTURED BY THE COM- 

 MERCIAL GEAR CURRENTLY EMPLOYED. AGE-FREQUENCY COMPOSITION OF THE 

 POPULATION HAS NOT YET BEEN DETERMINED. 



THE ANALYSIS OF MORPHOMETRIC DATA HAS TO DATE REVEALED NO DISTINCTIVE 

 RACES IN THE POPULATION. 



ST . HELENA BAY : THE ST. HELENA BAY AREA IN WHICH THE COMMERCIAL FISH- 

 ERY CURRENTLY OPERATES REPRESENTS AN AREA IN WHICH ALL THE ENVIRON- 

 MENTAL FACTORS, BOTH PHYSICO-CHEMICAL AND BIOLOGICAL, ARE FAVORABLE 

 FOR FINAL CONDITIONING FOR BREEDING. THIS AREA FAVORS SCHOOLS IN 

 PROGRESSIVE STAGES OF SEXUAL DEVELOPMENT, ENTERING AND DEPARTING FROM 

 IT IN SUCCESSION FOR THE SPAWNING GROUNDS WHEN PRESPAWNING CONDITION- 

 ING HAS ADVANCED TO THE CRITICAL STAGE IN EACH CASE. IT APPEARS THAT 

 THE FINAL SCHOOLS ENTER THE AREA SOMETIME IN OCTOBER AND PRACTICALLY 

 A COMPLETE DEPARTURE OCCURS SOMETIME IN NOVEMBER. THE ROTATIONAL 

 PROCEDURE IS RESUMED SOMETIME IN MARCH OR APRIL IN RELATION TO RE- 

 ESTABLISHMENT IN SEASONAL TIME OF THE FAVORABLE PHYS I CO-CH EM I CAL/b I 0- 

 LOGICAL NORM. 



CONDITION OF THE FISH FOR COMMERCIAL USES: IN REGARD TO THE CONDITION 

 OF THE FISH FOR INDUSTRIAL PROCESSING, INCLUDING CANNING AND MEAL AND 

 OIL PRODUCTION, IT SEEMS TO BE CLEAR THAT A PROGRESSIVE RECESSION OC- 

 CURS, BOTH IN MASS-PREVALENCE AND INDIVIDUAL STATE, COMHENCING IN LATE 



