July 1966 



COMMERCIAL FISHERIES REVIEW 



49 



The combination of unfavorable fishing 

 weather and few sightings would indicate that 

 at that time of year the area holds little prom- 

 ise for a tuna fishery. 



Between March 8 and 26 a fishery-ocea- 

 nography survey along the north coast of 

 Venezuela from Trinidad to Curacao was car- 

 ried out. Heavy seas prevailed during the 

 first portion of the survey, making it difficult 

 to sight fish. In general, it was too rough to 

 allow the fishermen in the racks for bait fish- 

 ing. As a result most fish caught during the 

 first portion of the survey were taken on jig 

 lines. On March 16, two 35-pound yellowfin 

 were caught by that method. 



A total of 14 scattered schools of skipjack, 

 4 of yellowfin, and 3 of little tuna were sighted 

 during the survey --all were too small for 

 commercial bait or purse -seine fishing. A 

 total of 2 yellowfin, 8 skipjack and 7 blackfin 

 tuna, and 1 frigate mackerel ( Auxis sp.) was 

 caught, mostly on jig lines. Many large breez- 

 ing schools of blackfin tuna and frigate mack- 

 erel were seen on Margarita Bank, located 5- 

 7 miles off the harbor of Caracas, Venezuela. 

 The blackfin were in close association with 

 pods of baleen whales feeding on the rich con- 

 centration of plankton over the Bank. Flying- 

 fish and dolphin were numerous in these wa- 

 ters and more than 40 dolphin were hooked on 

 jigs. The combination of rough weather and 

 few fish indicated that the coastal and oceanic 

 areas north of Venezuela during the month of 

 March hold little promise for a commercial 

 tuna fishery. 



Between April 2 and 15 a fishery-oceanog- 

 raphy survey from Curacao to Miami was car- 

 ried out. Most of the effort was concentrated 

 in the Lesser Antilles, especially in the area 

 west of the islands of St. Vincent and St. Lucia. 

 More than 20 schools of skipjack were sighted 

 in a period of 10 days. Biological samples 

 were collected from 276 skipjack sampled 

 from these schools; this number resulted from 

 attempts to catch a maximum of 25 fish from 

 each school sighted and fished. Most fish were 

 less than 12 pounds and many had nearly ma- 

 ture gonads. All schools sighted were of com- 

 mercial quantity and behaved in a schooling 

 fashion believed to be particularly well suited 

 to the purse -seine method of fishing. 



The western side of the Lesser Antilles is 

 characterized by turbulent eddies formed where 

 the islands intercept the westward moving arms 

 of the Guiana Current. An intensive grid of 



bathythermograph and hydrographic, as well 

 as biological, stations was occupied in a 550- 

 square-mile area to determine time -space 

 changes in the distribution of these eddies. 

 Preliminary analysis of the distribution of 

 temperature reveals that the eddies may be 

 relatively permanent features and may act as 

 mechanisms for biological enrichment, de- 

 pending upon the direction of eddy rotation. 



Measurements of temperature, salinity, in- 

 organic phosphate, and oxygen were taken at 

 depths down to 500 meters (1,640 feet) using 

 standard Nansen bottle casts. Plankton sam- 

 ples, measurements of primary productivity 

 using C-14, neuston net tows, and nightlight 

 samples were taken. A continuous daytime 

 watch was maintained for fish schools, birds, 

 and mammals. The fish caught were sampled 

 for length, weight, and sex determination; 

 stomach contents, gill rakers, and gonads 

 were preserved for later study. Samples for 

 biochemical analysis also were taken from the 

 fish. These included eye lenses, external med- 

 ian flank muscle, gonad, heart, liver, caecal 

 mass, and stomach. Blood samples were 

 taken from 100 tuna for serological analysis 

 by the U. S. Bureau of Commercial Fisheries 

 Biological Laboratory, Honolulu, Hawaii. 

 Tissue samples were collected for analysis of 

 possible insecticide concentrationby the Bu- 

 reau's Biological Laboratory at Gulf Breeze, 

 Fla. Miscellaneous fish specimens for syste- 

 matic studies were collected at a number of 

 locations; shore collections were made at the 

 Marquesas Keys in Florida. 



INVESTIGATION OF THE BIOLOGY AND 

 ECOLOGY OF BAIT FISHES: An unsuccess- 

 ful attempt was made to collect bait fish (from 

 January 24-27) in the vicinity of Fort Myers 

 Beach, Fla., but bad weather hampered oper- 

 ations. The few fish attracted to the night 

 light were harassed by large cobia ( Rachy - 

 Gentron canadum). 



Live bait was obtained (February 11-12) 

 at the U. S. Naval Base, Trinidad, by fishing 

 a lampara net during the day. The bait in- 

 cluded Spanish sardines ( Sardinella sp.), her- 

 ring ( Harengula sp.) and juvenile leatherjack- 

 ets ( Oligoplites saurus ). The bait survived 

 only 3 days because of extremely rough 

 weather. 



A total of 150 scoops of Spanish sardines 

 was purchased (March 14) from fishermen 

 in the Gulf of Cariaco, Venezuela. An addi- 

 tional supply was obtained at Punta de Araya. 



