FISH EGGS AND LARVAE IN THE PLANK.TON SAMPLES

Transcription

1 FISH EGGS AND LARVAE IN THE PLANK.TON SAMPLES GRACE L. ORTON INTRODUCTION available for some of the species from pub This paper summarizes the data on fish lished accounts based on the very extensive eggs and larvae from the plankton Marine Life Research ( MLR) collections, taken on four cruises in EE& Station plans and this evidence gives some measure of for these cruises are shown in Figure. In the significance of the results. Thus, the data, especially on the sardine, carangid Tables to 3 the eggs and larvae are listed by taxonomic groups (insofar as they fishes, and hake, can be compared with can be identified from present knowledge ), detailed work on these fishes in recent by cruise, papers by Ahlstrom ( 954), Ahlstrom and and by approximate distance Ball ( 954), and Ahlstrom and Counts offshore. ( 955), respectively. Additional data for The tables arc based on a standardized comparison are given in the progress relist of the major taxonomic groups of telcost fishes that were found rcpresentcd in the ports of CCOFI. For the most part the findings are in rather close agreement with material. In addition, the list provides published MLR results, but the scorpaenid space for a number of other groups (notably larvae show a considerable departure. This the tunas and blcnnioid fishes) for which indicates the riced for caution in intcrprctit seems desirable to cmphasizc absence in ing these limited data. these collections. The tables on geographic distribution are based on a somewhat arbi SARDINES trary and diagrammatic zonal pattern (Fig. >7 recording eggs and larvae occurring Sardine eggs were taken on all four within areas approximately 00, 200, 300, cruises, and larvae were taken on all but and over 300 miles offshore. Cruise 4. The eggs were most abundant on Large numbers of eggs and modcrate Cruise (April); total numbers of larvae numbers of larvae are recorded as uniden taken on Cruises to 3 were relatively contified. The wellknown difficulties of iden stant (Table ). The actual total numbers tifying marine fish eggs and larvae need taken per cruise appear to be more signifinot bc elaborated, but it should be pointed cant for compariso,n than the numbers per out that the bulk of the unidentified eggs sample per cruise, since the definitely idenis one general type which, on further study, tifiablc sardine material was all taken north will probably prove referable to the sto of 25 N regardless of cruise track and nummiatoid genus Powerin, the dominant elc ber of. Roth eggs and larvae were mcnt in the larval collections. most abundant within 00 miles of the short and fell off sharply to the seaward COMMERCIAL FISIIES (Table 2). One egg was recorded from the 3OOmile zone and one from outside The plankton collections contained rela 300 miles. tively small numbers of eggs and larvae The data on sardine eggs and larvae identifiable as groups of commercial interagree with the MLR results in both seasonal est. The occurrence of these fishes is summarizcd in Table 3, which lists numbers and geographic occurrence. Ahlstrom rcper sample per cruise and per NOmile ported: Spawning off southern California interval offshore. and adjacent Baja California may occur at One could question whether the results considerable distances from shore. Sardine of this small series of cruises give an ade eggs have been collected about 250 milts quatcly represcntativc picture of the occur offshore, and larvae at even greater disrencc and distribution of these fishes in the tanccs; but large concentrations of eggs are area. However, supporting evidence is seldom taken farther from shore than 50 xxxii

2 ... FISH EGGS AND LARVAE IN THE PLANKTON SAMPLES xxx FIG.. Stations at which fish eggs and larvae were collected during 4 longline cruises in 954. (Cruise, April; Cruise 2, May; Cruise 3, July and August; Cruise 4, Scutcrnber and October.) The arbitrarv arcas based on distance from shore arc indicated by the broken lines. miles. In summarizing data on the spawning season, he reported: Sardine eggs have been collected during every month of the year off central Baja California, although the period of major abundance has been limited to the months of February through May. ANCIIOVLES Some anchovy larvae were taken on all four cruises, but eggs were obtained only on Cruise 3. The larvae were very abundant on Cruise (April), and the numbers fell off sharply and progressively on the later cruises. Nearly all the larvae ( 495) were taken within the loomile zone, very few (5) in the 2OOmile zone, and none farther offshore (set Table 2). Information concerning the distribution of anchovy larvae taken on the MLR cruises in 95 and 952 was mapped and briefly discussed in CCOFI Reports for 952 (p. 40) and 953 (pp. 34 and 35). Although the larvae were more abundant at inshore stations in both years, some occurred as far as 300 miles offshore in 95 and as f ar out as 200 miles in 952. In 95, spawning off central Baja California was most abundant from February through May, but some spawning occurred throughout the year. It is evident that anchovies

3 Unidentified , , , , , r g si (?) i Clupeoids ( Sardines ) ( Anchovies ) Alepocephalids Argentinids Eels Stomiatoids Myctophids Iniomous fishes Synentognaths (Saw) (Flying fish) Codlike fishes (Hake) ( Microurids ) ( Misc. ) Allotriognaths Flatfishes Berycoids ( Melamphaeids ) Typical percoids ( Serranids ) Muoiloids (Barracuda) Carangiforms ( Carangids ) ( Dolphins ) Scombriforms (Mackerel) ( Tuna ) ( Gempylids, etc. ) Bramids Tetragonurus Scorpaeniforms ( Scorpaenids ) ( Cottids ) ( Triglids ) Chiasmodontids CalIionymids Blennioids Gobies Ceratioids , : lo: , E l(?) (?)

4 TABLE 2. Summary of eggs and larzjae tabulated by zones offshore for all four PaolinuT cruises combined (totals and numbers per sample) 00 miles 200 miles 300 miles Over 300 miles Eggs Larvae Eggs Larvae Eggs Larvae Eggs Larvae Per Per Per Per Per Per Per Per Total sample Total sample Total sample Total sample Total sample Total sample Total sample Total sample Ii M g PJ Clupeoids (Sardine) ( Anchovies ) Alepocephalids Argentinids Eels Stomiatoids Myctophids Iniomous fishes Synentognaths (saw) ( Flyingfish ) Codlike fishes (Hal ( Macrourids ) ( Misc. ) Allotriognaths Flatfishes Berycoids (Melamphaeids) Typical percoids ( Serranids ) Muoiloids (Barracuda) Carangifonris ( Carangids ) ( Dolphins ) Scombriforms (Mackerel) ( Tuna ) (Gempylids, etc.) Bramids Tetragonurns Scorpaeniforms ( Scorpaenids) (Cottids) ( Triglids ) Chiasmodontids Blennioids Gobies Ceratioids (?) : 240*: : , , (?) cr: z!z M , r F % cn l(?) (?) (?) l(?) x tj

5 xxxvi GRACE L. ORTON can occur substantially farther offshore 98 to 99.5% of the larvae were taken during than found in the present material. this 5month period. HAKE SCOMBROID FISIIES Hake eggs and larvae were taken only No eggs or larvae identifiable as tuna on the first two cruises, predominantly on were found. However, some of the other Cruise (April). None were taken farther scombroid fishes were represented. Very offshore than 200 miles and none farther small numbers of eggs and larvae of Pacific south than 27 N. mackerel were taken on Cruises 2 and 3 These results accord closely with those of the more extensive MLR studies. Ahl Strom and Counts ( 955) found hake larvae abundant only from February to April; in both 95 and 952, about 98% of all hake larvae were taken in this period. In both years about 88% were taken in the area from Point Conception to San Quintin, Baja California. Off southern California they were taken as f,ar as 350 miles offshore, but in both years the area of concentration narrowed to the southward to a zone much closer inshore. JACK MACKEREL Carangid eggs and larvae were taken only on the first two cruises (April and May). They were most abundant in the 200mile zone, with lesser numbers at 300 miles and over 300 miles. Furthermore, none were taken south of 25 N. It is possible that all the carangid eggs and larvae taken were jack mackerel, but early stages of this fish have not yet been clearly differentiated from related carangids that might occur in the area (e.g., species of Decnpterus ). The occurrence of carangid eggs and larvae agrees well with the MLR results on jackmackerel larvae. Ahlstrom and Ball ( 954) found that jackmackerel larvae were concentrated in a broad area well offshore from central California southward to central Baja California, with small numbers taken as far south as the level of Magdalena Bay, The larvae were most abundant in a broad area about 80 to 240 miles offshore, but continued to appear as far seaward as the MLR cruises sampled, although there was a steady decrease in abundance beyond 240 miles. The larvae were most abundant from March through July; about ( May to August), occurring then in the loomile and 300mile zones (see Tables and 3). The numbers are too small to be very meaningful alone, but can bc compared with the data on Pacific mackerel larvae taken by MLR in 952 (CCOFI Report, 953, Fig. 26, pp. 38 and 39). That report also indicates the relatively small numbers of larvae taken and their spotty distribution as far seaward as 300 miles. Off central Baja California on the 952 MLR cruises, the larvae were found to be most abundant in April and May, but some spawning occurred during most of the year. Eggs and larvae of at least one species of gempylid arc represented in our collection ( see Tables to 3). Large numbers of gempylid eggs were obtained on Cruises 3 and 4 from inshore stations near and southward from Point Eugenio, in the general region that closely corresponds to an important area of upwelling mapped in the CCOFI Progress Report for 953 ( Fig. 4, p. 0). MISCELLANEOUS COMMERCIAL FISHES Several additional telcost groups that include species of commercial or sport fishing interest were represented. Flatfish larvae were taken on all four cruises but in largest numbers on Cruise. Nearly all ( 334) were taken within the loomile zone, only 35 in the 200mile zone, and only one in the 300mile zone. Their heavy concentration inshore is to be expected for flatfishes in general. There is some suggestion of seasonal concentration, but the flatfishes comprise many species with poorly known life histories, and those represented may well differ significantly in spawning season. The contained a single barracuda l arva, taken on Cruise 3, close inshore south of Point Eugenio.

6 FISII EGGS AND LARVAE IN THE PLANKTON SAMPLES xxxvii TABLE 3. Summary of eggs ancl larvae of commercial groups and of some of the dominant noncommercial groups Sardine eggs Sardine larvae Anchovy eggs Anchovy larvae Samy eggs Saury larvae Hake eggs Hake larvae Flatfish larvae I3arracucla larvae Carangid eggs Carangid larvae Dolphin eggs Dolphin larvae Pacific mackerel ew larvae Scorpaenid larvae 6 cz:ll I Argentinid eggs Argentinid larvae 8.6 S tomiatoid larvae 2.6 Myctophid larvae 9.33 Numbers per sample per cruise Numbers per sample per zone offshore 39 Cruise 2 May 42 2 Cruise Scpt October miles = Noncommercial Groups milts over milts miles Small numbers of dolphin eggs and larvae were taken, chiefly on Cruises 3 and 4. The eggs were most abundant in the loomile zone, but a few were taken at 200 and 300 miles. Larvae occurred in the NO and 300mile zones. There has apparently been no work published on the early life history of the dolphins in the eastern Pacific. The seasonal and zonal distribution suggests that spawning of these fishes may bc associated with relatively warm water and may extend to moderate distances offshore. At least two kinds of scorpaenid larvae were present. They probably represent species of Scorpnenn and Sebmtodes. Most were taken on Cruise ( April) from the NOmile zone. This might suggest sharp seasonal and offshore limitations, but the much more extensive MLR data do not bear this out. Thus the CCOFI Progress Report for 952 (Fig. 5, p. 43) maps the scorpaenid larvae collected in 95 and records that they were widely distributed in every month and that they were taken persistently as far as 300 miles offshore. NONCOMMERCIAL FISHES The many groups of noncommercial fishes taken are indicated in the tables. The three groups that dominate the the argcntinids, stomiatoids, and myctophids arc included in Table 3 for comparison with the fishes of direct commercial interest. A stomiatoid genus, Power@ is the most conspicuous form throughout the collections. These larvae show a steady incrcasc in numbers throughout the summer, and a heavy concentration far offshore, from 300 miles outward. The nearly uniform distribution of myctophid larvae, both in season and in distance offshore, is noteworthy,

7 ... XXXVlll GRACE L. ORTON REFERENCES AIKSTROM, E. H Distribution and abundance of egg and larval populations of the Pacific sardine. U. S. Fish Wildl. Serv., Fish. Bull., 93: 8340., AND 0. P. BALL Description of eggs and larvae of jack mackerel (Trachums svmm&icus) and distribution and abundance of larvae in 950 and 95. U. S. Fish Wildl. Serv., Fish. BulI., 97: , AND R. C. COUNTS Eggs and larvae of the Pacific hake (Merluccius pro LEuctus). U. S. Fish Wildl. Serv., Fish. Bull. 99 : CALIFORNIA COOPERATIVE OCEANIC FISHERIES IN VESTIGATIONS Progress Report Jan lary 95 to 30 June 952. State of California Dept. Fish Game, Mar. Rcs. Comm., 5 pp. * 953. Progress Report July 952 to 30 June 953, State of California Dept. Fish Game, Mar. Rcs. Comm., 44 pp.