FISHERY BULLETIN; VOL, 78, NO. 3 



Live 

 SL, HL, BD, ED 



Laboratory 

 Preserved 

 Formalin 

 Alcohol 



Net Treatment 



minutes: 



_^ Preserved 



Formalin 

 Alcohol 



("Field Collected' 



Figure L — Experimental design. Four measurements of larval 

 northern anchovy were taken to estimate shrinkage during han- 

 dling treatments: standard length, SL; head length, HL; body 

 depth at the anus. BD; and eye diameter, ED. 



for northern anchovy ); body depth at the anus; and 

 eye diameter. I kept track of individual larvae 

 during all treatments and determined body part 

 shrinkage on an individual basis. The same larva 

 could be measured as many as six times; e.g., a 

 "field-collected" larva was measured live, after 

 four time intervals in the net, and again after 

 preservation. However, not all net-treated larvae 

 were measured for four time intervals. I used sev- 

 eral preservatives: Bouin's fixative, usually used 

 for histological studies; 57^ buffered Formalin- 

 (2.2% formaldehyde), the standard ichthyoplank- 

 ton-survey preservative (Ahlstrom 1976; Smith 

 and Richardson 1977); and SOVc ethyl alcohol, pre- 

 servative for otoliths (Methot and Kramer 1979). 

 In treatments (2) and (4), larvae were kept in pre- 

 servative for 4-5 wk before remeasuring. 



As an example of laboratory handling proce- 

 dures, I have included results from ongoing 

 studies on morphology of jack mackerel and 

 Pacific barracuda, Sphyraeria argentea, larvae. 

 Eggs of jack mackerel and Pacific barracuda were 

 collected 30-50 km off the coast of southern 

 California in June and July 1977, and rearing 

 procedures were the same as for northern anchovy. 

 Laboratory handling in this study consisted of 

 pipetting live larvae 1) onto a slide for measure- 

 ment and 2) into preservative. Time spent han- 

 dling was an important factor affecting shrinkage. 

 Larvae shrink during the measuring process. In 

 this study, all live and laboratory shrinkage mea- 



surements include about a 30 s handling time. 

 Some scientists measure laboratory-reared larvae 

 only after preservation; these larvae are probably 

 handled -30 s. 



In his paper on the quality of field-collected fish 

 larvae, Ahlstrom (1976) noted several conditions 

 that damaged specimens: fast net speeds, high 

 temperatures, and increased time in the net. Dur- 

 ing standard ichthyoplankton surveys, larvae in 

 the nets could be damaged by abrasion for up to 20 

 min before preservation, the net is towed for 20 

 min, ascending 15 min, and then the collected 

 sample is washed down into the cod end and pre- 

 served (Ahlstrom 1976; Smith and Richardson 

 1977). Considering these variables, I designed a 

 net treatment to simulate shipboard procedures. 

 For the treatment, seawater was circulated over a 

 single larva in a submerged net container. (Small 

 larvae, 4-7 mm, were treated in groups of 10.) To 

 obtain conservative results, the water tempera- 

 ture was cool, 13° C, and the net-treatment time 

 varied: 5, 10, 15, and 20 min. The net-treatment 

 time included the pipetting and measuring as well 

 as the time in the net. After net treatment, larvae 

 were preserved; I equate these net-treated and 

 preserved larvae with field-collected larvae (Fig- 

 ure 1). 



RESULTS 



Live Body Parts 



Head length, body depth, and eye diameter were 

 examined as functions of standard length for live 

 northern anchovy larvae (Figure 2, Table 1). On a 

 double logarithmic scale (Figure 2) both head 

 length and body depth relationships show curva- 

 ture, but the eye diameter relation appears to be 

 nearly linear. According to Zweifel,^ the simple 

 allometric body part relationships used for 

 juvenile and adult fish are not adequate for de- 

 scribing body part relationships of larval fish, ex- 

 cept for very limited ranges of size or age. There- 

 fore, I assumed that the larval body proportions (y) 

 change continuously during growth, varying ac- 

 cording to a nonlinear allometric growth model, 



Iny = a - bic-lnx)''. 



''Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



^Zweiful, J. T. Equations of growth and allometry in larval 

 and adult fish. Unpubl. manuscr Southwest Fisheries Center La 

 JoUa Laboratory, National Marine Fisheries Service, NOAA, 

 RO. Box 27L La Jolla, CA 92038. 



686 



