FISHERY BULLETIN: VOL. 80, NO. 4 



is the product of the density of fish and the 

 growth of the individuals (Ricker 1946). 



An HP9100A program was developed with the 

 aid of Joel Weintraub (California State Univer- 

 sity, Fullerton) to calculate the production of 

 each recognizable size-class of the common spe- 

 cies, those which were collected in at least 2 con- 

 secutive months at each station. The model used 

 was that proposed by Ricker (1946) and modified 

 by Allen (1950) and is calculated as follows: 



where G = 



P = GB 



log, w 2 - log, Wl 

 At 



is the instanta- 

 neous coeffi- 

 cient of growth; 



B 



Z = 



Bi(J : - z -l) 

 G-Z 



is the average biomass 

 over the time interval; 



-(log, N 2 - log, Ni) 

 At 



is the instan- 

 taneous coef- 

 ficient of population change of the immediate 

 sampling area (station) attributable to mortality 

 and migration; 



B is the biomass density of fishes at t\\ w u W2 are 

 the mean weights of individuals at time t\ and fo; 

 and N\, N 2 are the numbers of fishes present at h 

 and t%. G—Z is the net rate of increase in biomass 

 during At (1 mo). 



The model assumes that production data need 

 not be corrected for immigration and emigration 

 of fishes in and out of the sampling area, pro- 

 vided the density and growth by size-class are 

 estimated frequently enough to accurately assess 

 the abundance and growth of fishes actually in 

 the sampling area (Chapman 1968). 



In the present study, growth increments were 

 estimated from length-frequency data for fishes 

 from all three stations each month for each size- 

 class. The length data, therefore, were represen- 

 tative of the entire population of the size-class in 

 the upper Newport Bay and served to minimize 

 the effects which localized movements into and 

 out of a particular station have on monthly 

 growth values. The average weight, w, of a size- 

 class per month was calculated as follows: 1) Dry 

 weight equivalent for the median length in a size 

 interval (5 mm intervals) was determined using 

 standard length to dry weight curves for each 

 common species; 2) the proportion (range 0-1) of 



individuals represented in the size interval was 

 multiplied by the dry weight equivalent for the 

 interval; 3) the products were then summed for 

 all size intervals contained within the particular 

 size-class of the species yielding an average 

 weight, w. This method proved to be more accu- 

 rate than simply taking the mean length of the 

 entire size-class and determining the dry weight 

 equivalent. 



The "best estimate" of biomass density {B) for 

 each discernible size-class was determined in the 

 following manner: 1) The biomass density (wet 

 weight) derived from the method (BS, SS, DN, or 

 SE) shown to be most effective at sampling the 

 particular species was used. Table 1 lists the spe- 

 cies with corresponding collecting gear ranked 

 by their effectiveness at capturing the species. 

 This list is based on a comparative study of the 

 sampling methods (Horn and Allen footnote 2); 

 2) if, as in a few cases, the biomass estimated was 

 inordinately high, due to a large catch in one 

 replicate sample, the estimate defaulted to the 

 next gear type in the rank order; 3) the biomass 

 estimate in wet weight was converted to a dry 

 weight (DW) equivalent by a conversion factor 

 determined for each species and entered into the 

 production model as B\ (g DW/m 2 ). Production is 

 the total of all positive values for size-classes dur- 

 ing a time period (1 mo in this case) at each sta- 

 tion. Negative values were due to sampling error 

 and emigration and were not included in produc- 

 tion estimates. 



Large individuals (>100 mm SL) of Mugil 

 cephalus were not included in production esti- 



Table 1.— Methods for best estimate of spe- 

 cies densities ranked by effectiveness (Horn 

 and Allen text footnote 2). BS = bag seine; 

 SS = small seine; DN =dropnet; SE =square 

 enclosure. 



Species 



Methods ranked by 

 effectiveness 



At her mops allinis 

 Fundulus parvipmnis 

 Clevelandia ios 

 Anchoa compressa 

 Gambusia allinis 

 Cymatogaster aggregala 

 Gillichthys mirabilis 

 Anchoa delicatissima 

 Mugil cephalus 

 Engraulis mordax 

 Leuresthes tenuis 

 Ouielula ycauda 

 llypnus gilberti 

 Syngnathus spp 

 Hypsopsetta guttulala 

 Lepomis macrochirus 

 Lepomis cyanellus 

 All other species 



BS, SS 

 SS, BS 

 SE. SS, DN 

 BS, SS, DN 

 SS, BS 

 BS, DN, SS 

 SS, SE, BS 

 BS, SS 

 SS, BS 

 BS, SS 

 BS, SS 

 DN, SS 

 DN. SS 

 SS, DN 

 SS, DN 

 BS. SS 

 BS, SS 

 BS, SS 



772 



