Table 3. — -Results of tests to determine subsampling accuracy 

 for obtaining total counts of larral shrimp in plankton 

 samples 



Fraction of sample examined 



I Significant at .05 level; chi-squnre table value = 3.841. 



plankton hauls during both periods of increased 

 abundance. At 14-m. stations, however, larval 

 stages were encountered only during May to 

 September. Postlarval stages made up the en- 

 tire catch in February and March. Exclusion of 

 postlarvae from the catches, consequently, re- 

 sults in a unimodal trend in larval abundance 

 at the shallowest stations and a bimodal trend 

 at deeper stations. 



■• "Seasonal abundance, size distribution, and spawn- 

 ing of penaeid shrimp in the northwestern Gulf of 

 Mexico," by William C. Renfro and Harold A. Brusher, 

 Bureau of Commercial Fisheries Biological Laboratory, 

 Galveston. Tex. 



The difference between depths in timing of 

 peak larval abundance is believed caused by the 

 bathymetric distribution of the white and 

 brown shrimp, which constitute about 98 per- 

 cent of the total commercial shrimp landings 

 from this area. Lindner and Anderson (1956), 

 reporting on the bathymetric distribution of 

 white shrimp in Louisiana and Texas waters, 

 indicated that although a few adults may be in 

 water deeper than 27 m., the bulk of the popu- 

 lation is in shallower water. The spawning 

 period in May to August, indicated by the oc- 

 currence of larvae in our plankton hauls at 14- 

 and 27-m. stations, agrees closely with the 

 spawning season of white shrimp along the 

 Louisiana and Texas coasts postulated by Lind- 

 ner and Anderson (1956). 



Periods of increased larval abundance meas- 

 ured at 27-, 46-. and 82-m. stations reflect, we 

 believe, the spawning activity of brown shrimp. 

 The bathymetric distribution of adult brown 

 shrimp along the TexavS and Louisiana coasts 

 can be inferred from the statistics of commer- 

 cial landings supplied by the U.S. Fish and 

 Wildlife Service. These data reveal that al- 

 though brown shrimp concentrations vary sea- 

 sonally, the greatest number of adults usually 

 are in water 27 to 46 m. deep during the 

 fall. In addition, Renfro and Brusher (manu- 

 script in preparation),' who determined 



Tablk 4. — Monlhly ratrh nf I'mariix sjiji. by ilcpih. IHill 

 \ Number of shrimp per 100 m.' of water filtered | 



Month 



Depth and planktonic stage 



January 



14 meters: 



All stages... 



Nauplii 



Protoioeae.. 



Myses 



Postlarvae 

 27 meters: 



All stages. .- 



.Vauplil 



Protoiocac- 



Myses 



Postlarvae.. 

 46 meters: 



All stages... 



N'auplii 



Protoioeae., 



Myses 



Postlarvae.. 

 82 meters: 



All stages... 



N'auphi 



Protozoeac. 



Myses 



Postlarvae.. 



Feb- I March 

 ruary 



0.0 

 .0 

 .0 



.0 

 .0 



1.3 

 .0 

 .0 

 .0 



1.3 



.0 

 .0 

 .0 



1.4 

 .0 

 .0 

 .0 



1.4 



,9 

 .0 

 .3 

 .3 

 .3 



.0 

 .0 

 .0 



0.7 



.n 



.0 



.n 



2.1 



.0 

 .0 

 1.4 



3.3 



2.0 



April 



0.0 

 .0 

 .0 

 .0 

 .0 



Mav 



4.4 



2.2 



.0 



2.2 



.0 



.July 



10.5 

 2.9 

 7.6 



.0 

 .0 



4.5 



1.9 



2.6 



.0 



.0 



.0 

 .0 

 .0 



Cumulative total— all stages. 



.0 

 .0 



•0 

 .0 

 .0 I 



3.1 



.0 



.0 



1.7 



1.4 



Sep- 

 tember 



October | Novem- 

 ber 



1 Cumu- 

 lative 

 Decem- ' total 

 ber 



1.0 

 .6 

 .4 



.0 

 .11 



.';9.2 



41.9 



16.9 



.4 



.0 



303.9 

 13.7 



258.3 

 31.9 



.0 



105.1 

 3.4 

 95.4 

 2.1 

 4.2 



1.2 

 .0 

 .0 

 .0 



1.2 



31.0 

 4.3 

 2.7 



.5 

 23.5 



166.6 

 14.5 

 97.8 

 3.6 



50.7 



30.9 

 .0 

 .5 

 .0 



30.4 



19.1 



51.4 



469.2 



229.7 



.0 

 .0 



8.2 

 1.6 



278.2 

 28.2 



200.7 

 31.7 



17.6 



24.4 

 .0 



12.2 

 8.1 

 4.1 



312.4 



1.1 

 l.I 



.0 



.0 



31.0 

 14.6 



9.4 



4.2 



.1.7 



.0 

 .0 

 .0 

 .0 t 

 .0 



66.9 

 31.5 

 20.0 

 31.6 



808.9 

 81.6 



570.5 

 76.1 

 SO. 7 



166.1 

 3.8 



109.0 

 11.9 

 41.4 



34.1 



328 



DISTRIBUTION, SHRIMP IN GULF OF MEXICO 



