so wide a total area that sequential observa- 

 tions could seldom be made in one place. The 

 paragraphs that follow present trends and cor- 

 relations that are allowed by the data available. 



Bottom conditions.-- Lobsters were taken on 

 widely diverse types of bottom- -coral, rock, 

 sand, grass, and shell--but showed a prefer- 

 ence for spots near some type of concealment. 

 There was no correlation between the degree 

 of irregularity and the number of lobsters 

 caught, except that sets made on and im- 

 mediately adjacent to reefs caught fewer 

 lobsters than those from 50 to a few hundred 

 yards away from the reefs, in the reef forag- 

 ing area. Farther from the reef, on bottom 

 offering fewer hiding places than the inter- 

 mediate area, catch rates again dropped off 

 (fig. 16). 



Other factors of the bottom environment 

 associated with the presence or availability of 

 lobsters include bottom temperature and 

 salinity. Fishing was carried out over a total 

 temperature range of 68° to 85 F. and a 

 salinity range of 28 to 34 parts per thousand 

 (% ). In general, best fishing was experienced 

 in the narrower ranges of 83° to 85° F. and 

 31 to 32 "/„, . The effect of temperature on 

 trap catches was demonstrated graphically 

 during sets made off Panama City just before 

 and during a temperature decrease caused by 

 a sudden influx of cold (68° F.) water. Prior to 

 the influx, good catches were being made in 

 traps set in water having temperatures of 81° 

 to 82° F. As the cold water moved in, catches 

 fell off, and at a temperature of 68° F., 237 

 trap nights of fishing effort in 8-10 fathoms 

 failed to secure a single lobster. During the 



Sta.367 368 369 370 371 372 373 374 375 376 

 Catch 1 6 8 18 4 3 3 2 



Figure 16. — Depth recorder tracing of a "typical" stretch 

 of sea bottom with actual catches obtained from trap 

 fishing indicated above. 



same period, local boys were able to catch 

 spiny lobsters in unusually large numbers 

 when skin-diving and even while wading in the 

 shallow waters adjacent to the shoreline. 

 Templeman (1940), when discussing the effect 

 of cold water on the Americanlobster ( Homarus 

 americanus ) found in the waters off north- 

 eastern United States and Canada, stated, "In 

 very cold water, just above freezing point, 

 very little if any feeding occurs and few 

 lobsters can be trapped. As the water warms 

 up, feeding increases and the lobsters trap 

 readily." As spiny lobsters were being caught 

 by hand and spear adjacent to the shore- 

 line but not by traps in the 8- to 10-fa thorn 

 depth range it was apparent the water tempera- 

 ture drop of 17° F. may have stimulated the 

 lobsters to move inshore to more favorable 

 temperatures. 



In Panama, a common belief is that the Hum- 

 boldt or Peruvian Current brings cold water 

 into the Gulf of Panama during the dry season 

 (January-March) and causes the water tem- 

 perature drop mentioned here. In his study 

 of the oyster resources of Panama, Galtsoff 

 (1948) reports, "The presence of relatively cold 

 water in the western part of the Gulf of 

 Panama may suggest an upwelling along the 

 submarine valley west of the Pearl Islands .... 

 The suggestion that the difference in water 

 temperature in the Gulf of Panama and Chiriqui 

 Gulf is due to the influx of cold water from 

 the Humboldt Current or from its branch known 

 as the Galapagos Currents does not appear to 

 be sound, for the latter current extends north 

 only as far as 5° N. latitude and veers west." 



The presence of 31 to 32 %o salinities is 

 associated with areas receiving some runoff 

 from bordering river systems. Around 

 Montuosa Island, where conditions appeared 

 favorable for lobsters, but where no runoff 

 occurs, the catch was nil. 



In the Panamanian waters, temperature con- 

 ditions on the bottom proving optimal for trap 

 fishing are often found at depths of 4 to 5 

 fathoms, though this varies from point to point, 

 and the use of a thermometer for determining 

 bottom temperatures would be profitable in a 

 commercial venture. 



Illumination .- - Lobsters, being relatively 

 defenseless, appear to move about more readily 

 in the dark, and most fishing with traps was 

 planned to include one or more nighttime 

 periods. Comparisons of catches made on 

 bright moonlight nights with those on dark 

 nights without moon were made to determine 

 the level of illumination at which most ac- 

 tivity occurs. These, however, were not con- 

 clusive, owing in part to insufficient measure 

 of cloud cover and water turbidity. 



The trap environment .-- The theory behind 

 trap fishing is that the trap offers lobsters a 

 place of concealment, or a supply of food, or 



14 



