HORN: ABUNDANCE AND DIVERSITY OF MORRO BAY FISHES 



biomass) in the ith species. Calculations were 

 based on the use of natural logs (logp). 



The degree of specific change between samples 

 from one period to the next was calculated using 

 the percentage similarity index tPS ) developed by 

 Whittaker and Fairbanks (1958). Percentage 

 similarity ranges from 0, when two samples con- 

 tain no species in common, to 100, when the two 

 samples are identical in both species composition 

 and relative abundance. The index is calculated as 



PS = 100(1.0 - 0.5 V 



P.J) 



where P,q is the proportion of individuals 

 (biomass) in the ith species of sample a and P,^ the 

 same for sample 6. The basic data are the same as 

 are required for the calculation of//', i.e., the 



number or biomass of individuals in each species 

 of the sample. 



RESULTS 



A total of 11,627 fishes weighing 197,747 g were 

 captured in 36 seine hauls taken during the four 

 sampling periods (Table 1). Of the 21 species col- 

 lected, three species, Atherinops affinis, 

 Cymatogaster aggregata, and Leptocottus ar- 

 matus, composed almost 829^ of the total individu- 

 als. A fourth species, Engraulis mordax, contrib- 

 uted 11.2% of the total. Mustelus californicus, A. 

 affinis, and C. aggregata, accounted for nearly 84% 

 of the biomass collected. Leptoco^^j/.s armatus con- 

 tributed an additional 7% to the total biomass. 



For the four sampling periods taken together. 



T.'XBLE 1. — Number of individuals and biomass of fish species collected by beach seine in Morro Bay during four 24-h periods from 

 November 1974 to February 1976. The proportion that each species contributed to total numbers and biomass of each sampling period is 

 expressed as a percentage (%). (Species ranked according to total numbers for the four periods.) 



February 1976 May 1975 August 197 5 November 1974 Totals 



Individuals Biomass Individuals Biomass Individuals Biomass Individuals Biomass Individuals Biomass 



Species No. % g % No. % g % No. % g % No. % g % No. % g % 



Atherinops 



affinis 351 16.0 3.996 8.0 998 23 4 40,940 41.2 309 14 2 9.099 41 1 1,960 65.5 7.856 29.7 3.618 31.1 61.891 31 3 



Cymatogaster 



aggregata _ _ _ _ i 499 351 41.049 413 1,530 70.4 6.793 30 6 67 2.2 575 2.2 3.095 26.6 48.417 24.5 



Leptocottus 



armatus 1.668 76.2 2,063 41 644 151 3,649 3.7 272 125 3.725 16 8 196 6.5 4,444 16.8 2.780 23.9 13.881 7.0 



Engraulis 



mordax — — — — 909 21.3 1.532 1.5 2 09 3 — 397 13.3 280 1.1 1,308 11.2 1.815 0.9 



Funduius 



parvipinnis 25 1.1 50 0.1 1 — 10 — — — — — 229 7.6 728 27 255 2.2 788 04 



Syngnathus 



leptort)ynchus 18 0.8 24 05 35 0.8 200 02 18 0.8 111 0.5 94 31 850 3.2 165 1.4 1.185 0.6 



Ouietula 



y-cauda 26 1.2 49 01 64 15 158 02 27 1.2 94 04 2 0.1 2 — 119 1.0 303 02 



Micrometrus 



minimus 7 0.3 152 0.3 77 1.8 152 0.2 — — — — 6 0.2 149 0.6 90 0.8 453 0.2 



Lepidogobius 



lepidus 43 2.0 6 0.01 — — _——_ — — 1— 4— 44 0.4 10 — 



Embiotoca 



lacksoni — — — — II 3 171 0.2 9 4 340 1.5 17 0.6 1,238 4.7 37 0.3 1.749 9 



Atfierinopsis 



californiensis 25 1.1 3.659 7.3 1 — 280 0.3 1 0.05 230 1.0 5 2 1,296 4 9 32 0.3 5,465 2.8 



IVIustelus 



californicus 19 0.9 39,463 79.3 7 2 8,322 84 — — — — 3 1 7,296 27 5 29 3 55.081 27 9 



Dama//c/if/7ys 



vacca 1 0.05 240 05 19 0.4 2,390 24 — — — — 2 01 450 17 22 0.2 3,080 1.6 



Clupea 



fiarengus 1 0.05 88 2 — — — — — — — — 13 04 1,276 4.8 14 0,1 1.364 0.7 



Cleveland! a 



ios 2 0.1 2 — 2 — — — 1 005 2— 1— — — 6 0.1 4 — 



Hyperprosopon 



argenteum _ _ _ _ 3 0.I 121 — — — — — 1 — 50 0.2 4 — 171 0.1 



f^yliobatis 



californica ________ 3 0.1 1.760 7.9 — — — — 3 — 1.760 0.9 



Cittiarictithys 



stigmaeus 3 0.1 1 — — — — — — — — — — — — — 3 — 1 — 



Hypsopsetta 



guttulata _ _ _ _ 1 _ 320 03— — — — — — — — 1— 320 0.2 



Platichthys 



stellatus — — ______ 1 0.05 8— — — — — 1— 8 — 



Sebastes sp. 1 1 _ 1 — 1 — 



Totals 2,189 49,793 4,271 99,295 2,173 22,165 2,994 26,494 11,627 197,747 



Total species 13 16 11 16 21 



761 



