A Review of Survival Rates of Fish Eggs and Larvae in Relation to Impact Assessments
MICHAEL D. DAHLBERG
Introduction impact. The primary types of impact are ance (Edsall, 1975). Impact of entrain Pursuant to promulgation of the Fed impingement of fish on the intake screens ment or other perturbations may be eral Water Pollution Control Act Am and entrainment of smaller fish and eggs assessed by translation of egg and larval endments of 1972, Section 3l6b, electric into the cooling system. The size of the losses to the potential number of adults generating stations are required to dem intake screen mesh. usuallyYx inch. and they represent in the absence of entrain onstrate that cooling water intake struct size of fish determine whether the fish are ment. This is compared with a reference ures renect the best technology available entrained or impinged. The impingement such as stock size or commercial catch. for minimizing adverse environmental problem was reviewed by Hanson et a!. Implementation of models requires in (1977). The few published studies on formation on natural survival rates of the entrainment of fi'sh show that millions of species of concern, or at a minimum, what Michael D. Dahlberg is with the orthern En vironmental Services Division. NUS Corpora larvae are sometimes entrained daily by a survival rates may be expected among the tion, 1910 Cochran Road, Pittsburgh, PA 15220. plant during the period of peak abund- various groups of fishes.
ABSTRACT-Enormous fecundities of eggs. survival rates and short developmental per fishes are balanced by high egg and larval Amongfreshwater species, hatching success iods. mortalities resulting from natural interacting was low in unprotected eggs and high in The occurrence of brief critical periods of environmental stresses. Survival rates general species which exhibit parental care, construct high mortality was generally not supported ly increased inconsistently with age ofeggs and nests, but do not exhibit parental care, have when data were correctedfor larval extrusion. larvae. Few published studies provided the special protective mechanisms (y(!llow perch), The potentialfor high mortalin' to be offset by data needed to compare relative mortality and apparently in species which deposit eggs in compensatorv mechanisms is supported by among the three major developmental stages. vegetation. Among anadromous species, egg literature. A direct relationship of survival Mortality was greatest during the egg stage in survival in striped bass was particularly low in rates and development time suggested that the walleye and striped bass, but during the comparison to that in salmon. In the sea, high mortality rates were an expectedmechan postlarval stage in some marine species. Wide hatching success of demersal eggs was much ismfor regulation ofpopulalions having short ranges of egg survival for Atlantic herring, higher than in pelagic eggs. Survival ofyolk developmental periods. The availabilitv and northern pike, rainbow smelt, and walleye sac larvae was generally higher in marine and applicability of survival data to modeling of depend on whether egg production is basedon freshwater species than in anadromous spe impact is assessed. Many environmentalfac fecundity orfield counts, and whether survival cies. Survival of postlarvae was highest in tors should be considered when extrapolating is measured to a stage ofdrifting larvae or late freshwater species in relation to high daily survival data from one site to another.
March 1979 This paper represents a compilation of adequate data were available. Stages are able for relatively few species because available fish egg and larval natural sur classified as eggs, yolk-sac larvae (from avoidance of plankton nets increases vival rates and discusses problems asso hatching to complete absorption of yolk with size of larvae. It was neccessary to ciated with interpretation and use of sur sac), and postlarvae (from yolk-sac ab assume that postlarval survival rate was vival data, major sources of mortality, sorption to demersal or fully developed constant in order to complete the post survival rates associated with various juvenile).The survival curves are also nec larval survival curves for Pacific sardine I reproductive strategies, and the critical essary to examine the critical period con and yellow perch, as described in Table I. period concept. Effects of human cept, which is dependent on differences of This avoidance problem may be resolved perturbations and fish culture on survival slope within a curve rather than absolute by collection of postlarvae or juveniles rates are not considered. rates of mortality (Pearcy, 1962). ,Repre with trawls, as in studies of walleye sentat}ve survival data are presented, ei (Forney, 1976), winter founder (Pearcy Interpretation of ther bCy selection ofdata which appears to 1962), and Atlantic herring (Graham et Survival Data be typical ofdifferent years ofstudy or by a!., 1972), or with trap nets, as in north Since survival data are of little value averaging data for more than I year as ern pike studies (Forney, 1968). for modeling unless they are available for described in the footnotes. However, it is each of the developmental stages (Table not possible at this time to quantitatively I), it was necessary to construct survival account for all errors which may result curves and designate times of transition from bias in sampling methodology. 'Scientific names follow Bailey et al. (1970) to subsequent stages (Fig. 1-4) when Complete data on postlarvae are avail- except foreign names as listed in Table 4.
Figure I.-Survival curves for eggs and larvae of plaice during abnormal (P-AY) and typical (P-TY) years. Atlantic mackerel (AM), Japanese sardine (JS), jack mackerel (JM), Japanese anchovy (JA), and Black Sea anchovy (BSA). Incomplete segments are indicated by arrows. Yolk-sac stages indicated by parenthesis. See Tables I and 2 for sources. 5 ..~~+----.... 00 __+ o r o -:7----__+ ~969 P-AY 4 +----+--1:30days
1962
••• I o 0
:3
Q: W CD ~ , , ::::> Z
o • • • AM o 0 ...... S5days
o ...J-..-----r5----IOr-----,r5----Z'0---'Z5----3'O----3T5---'40----4'5----5TO---}55=---"-='=60 DAYS AFTER SPAWNING
2 Marine Fisheries Review Determination of survival of yolk-sac The use of age-related fecundity data by red water mites before the eggs were larvae generally required interpolation to calculate egg production is a possible sampled. Comparisons ofegg production between the egg and fully vulnerable source of error in the survival data for based on fecundity, and water body sam yolk-sac stages. This approach is nec northern pike (Forney, 1968), walleye pling yielded differences varying by a fac essary because the smallest larvae are (Forney, 1976), yellow perch (Clady, tor of 2.7 in striped bass (Polgar, 1977) generally extruded through nets in the 1976) and Atlantic herring off Norway and 3-34 in Clyde herring (Saville et aI., sea and are not fully planktonic in (Dragesund and Nakken, 1973). This 1974). However, these discrepancies were freshwater. This approach results in a may result in high estimates of egg pro thought to be a result of inadequate egg constant survival rate for smaller larvae duction if fertilization is not complete, sampling rather than incomplete egg instead of a more probable tendency for egg extrusion is incomplete as in salmon production. survival to increase during this period. (Johnson, 1965), or there are non Major Factors Which Egg production was indicated by nurtl spawning adults as in walleye (Forney, Influence Mortality Rates bers of ~ay-old eggs in plaice (Bannister 1976) and salmon (Johnson, 1965). Clady et aI., 1914) and 1.8·day-old eggs in jack (1975) indicated that the ratio of eggs The applicability of data from one mackerel (Farris, 1961). Actual egg pro deposited (based on field, counts) and region for another will depend on how duction was estimated by extrapolation potential egg deposition (based on similar the environmental conditions are to the spawning date, assuming a con fecundity) was low (15-34 percent) in a during the developmental periods. A stant survival rate among the early egg smallmouth bass population. However, number of the major factors which stages. this was possibly a result ofegg predation should be considered are discussed
Figure 2.-Survival curves for eggs and larvae of northern pike (NP), yellow perch (YP), walleye (W), Pacific sardine (PS), Black Sea mackerel (BSM), Atlantic herring in Norway (AH-N), round herring (RH), Atlantic thread herring (ATH), and scaled sardine (SS). Yolk sac stages indicated by parenthesis. See Tables I and 2 for sources.
4
X~YP
0: .,W ::0 :> z PS '"o -' 2
W -65 DAYS
ATH RH
S5
O,-L--, -,- -,- .---__--,r-____,_----,------'>fA~H.:...--.:.N:..--____,---__,_, --,, __,_, -,-, D ID 15 20 25 30 35 40 45 50 55 60 DAYS AFTER SPAWNING
March 1979 3 5
4
3 ----,-- ~ -----_~C58 -C If D .~~."'" ~" ~ ~"I--.. ~ o ~ ------~S6-P.M-1V SS-~
D.I -'--TI----,-I----,-I-----,-I-----,-I-----,-1-----,I:---~-_,---_,------r----,--...... :=~rrEV----r' o 5 10 /5 20 25 30 35 40 45 50 55 60 DAYS AFTER SPAWNING
Figure 3.-Survival curves for eggs and larvae of striped bass in Potomac River based entirely on net samples (SB-PM-N), in Potomac River with egg densities based on fecundity-at-age data (SB-PM-F), in Chesapeake and Delaware Canal (SB-C & D), and in Hudson River (SB-HR). Yolk-sac stages indicated by parenthesis. See Table I for sources.
below. Further quantification would when eggs were deposited on high 1973). Lethal dissolved oxygen levels lend more predictive value to this vegetation and free from silt (Galkina, were caused by high egg concentrations information. However, this would be 1971). in Atlantic herring (Jones and Hall, 1974), rather academic for predictive purposes Low now or low water levels were Pacific herring (Hempel, 1971), rainbow since extent of mortality is a function of detrimental to survival of eggs of salmon smelt (McKenzie, 1947), and salmon intensity as well as type of perturbation. (Warner, 196.1; McNeil, 1966), rainbow (Johnson, 1965). Quantitative estimates of the magnitude smelt (Rupp, 19(15) and Pacific herring Adverse effects of low water temper of mortality due to some factors such as (Soin, 1971), and larvae of northern pike ature on eggs have been shown with predation and starvation are almost (Hassler, 1970) and striped bass (Stevens, smallmouth bass (Kramer and Smith, totally lacking (May, 1974). 1977). Mortality often resulted from 1962), rainbow smelt (Rothschild, 1961), Substrate characteristics innuenced stranding of the eggs. Mortality of and northern pike (Hassler, 1970). Low egg survival in salmon (Larkin, 1977), Pacific herring eggs from desiccation water temperatures apparently reduced brook trout (HausJe and Coble, 1976), increased from 30 to 100 percent from the the rate of larval development and walleye (Johnson, 1961), and herring lower to the upper intertidal zone, and caused prolonged exposure to predation (Galkina, 1971). Siltation was a source of total mortality was 5 percent or less in in plaice (Bannister et aI., 1974), Pacific mortality in eggs of smallmouth bass subtidal areas (Soin, 1971). sardine (Murphy, 1961), Atlantic herring (Latta, 1975), lake trout (Youngs and Reduction of oxygen to a critical level (Graham et aI., 1972), northern anchovy Oglesby, 1972), salmon (McNeil, 1966) can cause mortality, e.g., salmon eggs (O'Connell and Raymond, 1970), and and Pacific herring (Galkina, 1971). (McNeil, 1966), brook trouteggs(Hausle walleye (Busch et aI., 1975). Colton Survival of Pacific herring eggs in and Coble, 1976), carp eggs (Nikolskii, ( 1959) reported mass mortality of marine subtidal water was about 100 percent 1969), and Baltic cod larvae (Grauman, fish larvae due to natural warming. A
4 Marine Fisheries Review 4
~ ~ 3 ,~
a: UJ ~ CD '" :l: :::> z 2 ~ 0'" -' ------+~ \\ r '\ t +WF \ / \
\ / \ PH-J \ / \\ \1 \ \ PH-B 0 0 20 30 40 50 60 70 80 90 DAYS AFTER SPAWNING Figure 4.-Partial survival curves for larvae of winter nounder (WF). Atlantic herring off Maine (AH-M), Pacific herring off Japan (PH-J), and Pacific herring off British Columbia (PH-B). Approximate days after spawning are indicated. See Tables I and 2 for sources.
rapid rise in water temperature adversely Black Sea anchovy (Dekhnik et aI., 1955). Dekhnik et al. (1970) noted that affected embryonic and larval survival in 1970), Black Sea mackerel (Dekhnik, postlarvae survive 10-18 days without herring (Rannak, 1971). (964), Japanese anchovy (Nakai et aI., food and concluded that " ...the food Storms and wave action caused 1955), Pacific sardine (Murphy, (961), factor cannot be considered a cause of the mortality of herring larvae (Wiborg, northern anchovy (O'Connell and mortality of fish larvae in the Black Sea." 1976) and cod eggs (Rollefsen, 1930). Raymond, 1970), winter flounder However, inadequate food increases Wave action caused stranding of I percent (Pearcy, 1962), walleye (Forney, 1976), vulnerability to other stresses and its of the yellow perch eggs in a lake (Clady, yellow perch (Tarby, 1974), northern effect on survival is mainly indirect 1976) and along with low temperature pike (Forney, 1968), pink salmon (Nikolskii, (969). (Johnson, 1965), and sockeye salmon was responsible for failure of largemouth Relationship of Survival Rates (Hartman et aI., (962). Occasional high bass nests (Kramer and Smith. 1962). to Reproductive Strategies Egg loss from nonfertilization is rates of predation on eggs and larvae of I n addition to specific environmental generally minimal and has been reported roach, rainbow trout, and other factors cited above, it is possible to make as about I percent in salmonids (Warner, freshwater species were noted by Paling some generalizations regarding the 1963) and 0.2-0.4 percent in Baltic herring ( 1971). survival rates of fish eggs and larvae in (Rannak, 1971). Egg loss from predation The hypothesis that lack offood causes relation to different reproductive has been reported in many species, larval mortality (Hjort, 1914) has been strategies and habitats. including Atlantic herring (Dragesund supported by studies of Atlantic and Nakken, 1973), Pacific herring mackerel (Sette, (943), plaice (Bannister Survival of Fish Eggs (Soin. 1971), smallmouth bass (Latta, et aI., 1974), Japanese sardine (Nakai and Hatching success of eggs is often low in 1975), and rainbow smelt (Rothschild, Hattori, 1962), Atlantic herring (Graham freshwater species which do not guard 1961). Predation and cannibalism were et aI., (972), pilchard (Karlovac, 1967), the demersal eggs. As little as 3 percent significant sources of larval mortality in and Japanese anchovy (Nakai et aI., survival from egg to migrant larvae has
March /979 5 been reported for the white sucker (Scott Egg survival was generally high in percent at high oxygen concentrations and Crossman, 1973). Forney (1976) freshwater species exhibiting parental for carp (Nikolskii, 1969), and 34-90 noted less than I percent walleye survival care (Breder and Rosen, 1966) and in percent for carp-bream (Nikolskii, 1969). through the swim-up stage in Oneida freshwater and anadromous salmonids Forney (1968) reported 77 percent Lake, with most of the loss probably in which cover the eggs with gravel (Table viability of northern pike eggs in a the egg stage. Walleye survival from 3). Parental care was a factor in the 49-94 regulated marsh but found that recently spawned eggs to a prehatching percent survival of white crappie eggs recruitment to pelagic yolk-sac larvae "eyed" stage was 2.4-25 percent on (Siefert, 1968), 26-33 percent survival to was only 16-19 percent. Protection various natural substrates (Johnson, emergence in smallmouth bass (Clady, afforded by the unique egg mass 1961). High egg mortality also occurs in 1975; Latta, 1975), and 94 percent envelopes contributes to high survival of the rainbow smelt: Rothschild (1961) survival of smallmouth bass eggs in a yellow perch eggs: Clady (1975) observed reported 24 percent egg survival (to 1-15 stream (Pflieger, 1966). However, only that viability was generally over 95 days before hatching) and 0.5 percent 44-55 percent of smallmouth bass nests percent. survival to the drifting yolk-sac stage; produced fry in large natural lakes Survival of unguarded demersal eggs McKenzie (1947) found that the hatching (La tta, 1975). of three marine species (Atlantic herring, rate was usually 0.8-1.8 percent; and High egg survival has been reported in Pacific herring, and capelin) was Rupp (1965) reported a mean hatch of 1.1 three freshwater species which spawn in generally considered to be over 90 percent in lakeshore spawners of this vegetation: 60-95 percent for northern percent (Baxter, 1971; Soin, 1971; species. pike (Franklin and Smith, 1963), 80-94 Rannak, 1971; Gj«lsaeter and Saetre,
Table 1.-Survival rates of eggs and larvae 0' marine, freshwater, and anadromou5 fishes. Footnotes are cross-referenced to Figures 1~5. Eggs Yolk sac larvae Postlarvae Total Survival Survival Survival Survival Fishes SurvIval Days per day Survival Days per day SIJrvival Days per day Survival Days per day
Marine Atlantic r.erring 1 0030 21 0.846 0.175 14 0.884 0050000 90 0.967 0.000263 125 0936 Atlantic mackerel' 0300 9 0.875 0.200 8 0.818 0.000067 60 0.852 0.000004 77 0.851 Atlantic thread herring3 0.660 0.8 0.595 0.400 4.9 0.830
Black sea anchovy 4 0.060 2.5 0.325 0.383 1.5 0.527 Jack mackerels 0.132 3.5 0.560 0.100 4.5 0.600 0.002182 49 0885 0.000024 57 0.830 Japa.nese sardine6 0.270 4 0.721 0.333 4 0.760 0.003333 62 0.913 0.000300 70 0.893 Pacific sardine7 0.360 3 0.712 0667 4 0.904 0008333 43 0.896 0002000 50 0883 Pla;cea 0.118 22 0.907 0.678 9 0958 0.00012.5 99 0.914 0.000010 130 0915 Round herring 9 0.380 2 0.616 0.250 8 0.841 Scaled sardine'o 0.120 0.8 0.071 0.106 7.5 0742
Freshwater Northern pike l1 0180 13 0.880 0572 8 0.931 0.291262 22 0.945 0.030000 43 0922 Walleye 12 0.005 24 0.800 0.132 9 0800 0.333333 31 0965 0.000060 64 0859 O.O~OOOO Yellow perch 13 0.259740 ~O 0.956 55 0.931
Anadromous Striped bass 14 0.009 2 0095 12 0.726 0.014000 41 0.901 0000003 55 0.793 Striped bass!S 0.003 2 0055 0.021 12 0.726 0.014000 41 0.901 0.000001 55 0.778 0.001000 0.926 Striped bass 16 0.100 2.5 0.398 0.100 12.5 0.832 0.100000 75 0.870 90 Striped bass l1 0.100 2.25 0.360 0.150 6 0.728 0.030000 52 0.935 0.000450 60 0.879
'Dragesund and Nakken (1973). Means of egg survival (0.01-0.05) and YOlk· sac "Houde (1977c). Means of survival to 5.5-mm prolarvae and 15.5-mm early larva survival (0.05-0.30). Egg survival based on fecundity-at-age data. (Fig. 2). postlarv.e. (Fig. 2) Postlarva data from Gushing (1974). Average values for 6-year study. limited to first II Forney (1968). Means of data for 2 years. Assume transformation to juvenile at 35 90 days (Fig. 4) mm and 43 days .fter spawning (Franklin and Smith, 1963). Actual egg survival was 2Sette (1943). Planktonic survival was 1x10-6 to 1x10-s, but 4x10-6 in his Figure 17 between the observed 77 percent viability and 18 percent survival to pelagic YOlk Apparent net avoidance in older larvae. (Fig. 1) sac larvae. (Fig. 2) JHoude (1977bL Means of survival to 5.5 mm yolk-sac larvae and 15.5 mm early 12Forney (1976). Mean values for 3 years in which cohorts Which were not postlarvae. (Fig. 2) augmented with yolk-sac larvae Survivors~ip of yolk-sac larvae (13.2 percent) 'Dekhnik (1963). Nikolskii (1969). Egg survival also given as 58 peroent (Dekhnik, estimated from relative numbers of 1- to 3-day-old larvae and 10-day-old larvae by 1960) and 19-40 percent (Pavlovskaia. 1955). (Fig. 1) assuming that differences in numbers of 10-day-old larvae in augmented and sFarris (1961). Means of data for 3 years. Survival for first month was approxim::ately unstocked cohorts resulted fro'1"' stocking Egg production based on fecundity. 01 percent all 3 years. Eight day period of yolk nutrition (Farris, 1960). (Fig. t) Trawled juvenile data used to complete the postrarvae ,urviv.1 segment (Fig. 2) 'Nakai and Hattori (1962. Table 6). Means of data for 3 years (Fig. 1) "Noble (1975). Survival values for davs 25 to 45 in 3 years. assumed to be constant 'Lenarz (1972) for abundance by length and Ahlstrom (1954) for ag~-Iength to demersal age (55 days). Survival and duration of earlier stages from Glady relationship. Samples collected at night and corrected for extrusion (Lenarz. (1975). (Fig 2) 1972). Egg survival (0.36) from Smith (1973). Four-day yolk-sac larva period "Polgar (1977. Table 2) Assumed exponential age distribution. Net samples only. (Ahlstrom. 1954). Daily survival rate for days 30-35 assumed to be constant through post-finfold (late PQstlarva) stage. (Fig, 3) through day 50. (Fig. 2) "Polgar (1977). As above. but with egg production based on fecundity-at-age data. 'Bannister et al. (1974). Data for typical year (1962). Yolk-sac larva period tollows (Fig. 3) Ryland (1966) (Fig 1) "Portner (1975). Assumed 0.100 survival for each stage. (Fig. 3) 'Houde (1977a). Means of survival to 5.5-mm yol'-sac larvae and 15.5-mm early "LMS (1975). Swartzman et al. (1977) Net samples only. through juvenile I (late oor,tlarvae. (Fig. 2) posllarva) stage. (Fig. 3)
6 Marine Fisheries Review 1974). Lower survival from spawning on Survival of pelagic cunner eggs was bass (Tables 1-3). Daily survival rates less suitable substrates or from dense estimated as 5 percent by Williams et a!. were 53-96 percent, 80-93 percent, and packing of eggs has been reported, but (1973). Survival of pelagic Baltic 73-83 percent, respectively. Survival of this is probably of little consequence in (Atlantic) cod eggs varied from I to 21 yolk-sac larvae of Danubian shad was comparison to predation on eggs percent in relation to dissolved oxygen, less than 10 percent (Dekhnik et a!., (Hempel, 1971). Dragesund and Nakken buoyancy (resulting from salinity) and 1970). Thus, there are no obvious (1973) concluded that egg loss from egg quality (based on size and fat differences in survival rates among the predation was 15-40 percent, and content) (Grauman, 1973). Survival of groups with the possible exception oflow mortality from hatching to recruitment pelagic Argentinean anchovy eggs was 7 survival in the anadromous species. 13 percent (Ciechomski and Capezzani, into the plankton was 83-95 percent in Survival of Postlarvae one herring population. An assumed 10 1973). There are additional observations percent hatch of demersal winter on viability of pelagic eggs, which Postlarval survival (Table I) was flounder eggs (Hess et a!., 1975) has not probably exceed actual survival rates, considerably higher In the three been verified. e.g., viability of pelagic pilchard eggs was
Data in Table I indicate that survival 50 percent off England and 48-87 percent Table 3.-Survlval rates 01 salmonids Irom egg to of pelagic eggs in the sea was relatively in other studies (Southward and Demir, hatching and emergence in nature. low (6-66 percent, mean 26 percent) 1974). Very low survival (0.3-10 percent) Egg to was also reported for the semibuoyant Species Hatching emergence although Murphy (1977) concluded that Atlantic salmon' 0.93 0.92 demersal eggs were more vulnerable to eggs of anadromous striped bass (Table Brook trout '0.80-0.93. '0.59, '0.79 '0.84 predation. However, survival of Black I). Brown trout Sea anchovy eggs has also been reported rainbow trout and Survival of Yolk-Sac Larvae chinook salmon' 0.71-0.97 0.91 as 58 percent (Dekhnik, 1960) and 19-40 Brown trout '0.89. '0.98 percent (Pavlovskaia, 1955). Survival of Survival of yolk-sac larvae ranged from Chum salmon' Over 0.80 001-0.25 Coho salmon '0.35-0.85 "0.26-0.54, pelagic Japanese anchovy eggs was 70 2.3 percent (winter flounder) to 68 '°0.85 "0.14-0.54 percent (plaice) in marine species, 13 Cutthroat trout '3 0.25-040 percent (Hayasi, 1967). Survival of pelagic Lake whitefish 14 Less than 0.13 sole eggs was 0.05 percent and 4.35 percent to 57 percent in two freshwater species, Pink salmon Over 150.80 "0.03-0.21 and 2.1 to 15.0 percent in striped "0.01-0.25 at two locations off England (Riley, 1974). Rainbow trout "042-0.92 Sockeye "0-0.79 "0.20. "0.085 Steelhead nO.86 "040
'Warner (1963). Survival to late eyed stage and emergence. 'Shetter (1961). Typical range. 'Hausle and Coble (1976). 'Brasch (1949). Upwelling favorable to survival. 'Hobbs (1940). New Zealand. 'Allen (1951) and Braum (1971). 'Kramer and Smith (1965). 'McNeil (1966). Typical emergence values. Table 2.-Survlval rates 01 Iish larvae and various larva and egg combinations 'Cloern (1976). Typical range. but 0-0.014 in Wisconsin. not shown In Tables 1 and 3. Footnotes cross-relerenced to Figures 1-5. "Briggs (1953). Survival "Moring and Lantz (1975). eer day Species Stage Survival Days "Koski (1966). Winter flounder' Yolk-sac larvae 0.023 17 0800 "Ball and Cope (1961). Postlarvae 0.319 28 0.960 "Van Oosten (1956). Pacific herring2 10-15 mm postlarvae 0.120 14 0.860 "McNeil (1966). 15-18 mm postlarvae 0.017 8 0.601 16Hanavan and Skud (1954). Tidal waters 18-28 mm postlarvae 0.500 19 0.964 "McNeil (1966). Typical values 10-28 mm postlarvae 0.0009 40 0.839 "Bjorn (1966). Planted eggs. Pacific herring3 Postlarvae 0.0005 20 0.684 "Krogius (1951). Postlarvae 0.025 11 0.715 wJohnson (1965). Survival to entry into nursery ground Pilchard· 2-20 mm larvae 0.004 <"Hartman et al. (1962). Survival to fry Qutmigration. Northern anchovy5 3-16 mm larvae 0.007 "Briggs (1953). Chub mackerel6 Eggs and larvae 0.005 23 0.721 "Coble (1961). Japanese anchovy 7 Eggs and larvae 0.0009 31 0.799 Black sea mackerel6 Eggs 0.207 1.1 0.239 Yolk-sac larvae 0.056 6 0.618 Smallmouth bass' Eggs to fry emergence 0286 10 0.882 Smallmouth bass lO Eggs to fry emergence 0.941 10 0.994
'Pearcy (1962). Data excludes 2.3-3.5 mm larvae. Translocation was minor Table 4.-Usl of common and scientific names ot foreign component of total 105585. Survival curve extrapolated to complete transformation IIshes cited In this paper. age in Figure 4. Common name Scientific name <'lizuka (1966). Data for postlarvae in 1959, representing three distinct survival slopes. Complete recruitment at 60 days after spawning. (Fig. 4) Argentinean anchovy Engraulis anchoita 'Stevenson (1962). Bimodal curve represents two broods of larvae. (Fig. 4) Black sea anchovy Engraulis encrasicholus 'Karlovac (1967). 2-20 mm larvae (Fig. 5). Black sea mackerel Trachurus mediterraneus 'Lenarz (1972). 3-16 mm larvae. Night samples corrected for losses through 0.55 Carp-bream Abramis brama mm mesh. (Fig. 5). Danubian shad A/osa a/osa 'Watanabe (1970). Spawning to day 23. Also called Japanese common mackerel Japanese anchovy Engraulis japonica 'Nakai et al. (1955). Survival from spawning to day 31. Mean of 3 years. (Fig. 1). Japanese sardine Sardinops me/anosticta 'Dekhnik (1964). From his table 3. (Fig. 2). Pilchard Sardina pi/chardus 'Clady (1975). Data for 3 years. Ten-day duration from Allan and Romero (1975). Roach Rutilus ruti/us Survival also reported as 27.6 percent (Latta, 1963). Sole Solea solea "Pflieger (1966) Stream population. Duration from Allen and Romero (1975).
March /979 7 100 days (10-12 mm) (Dragesund and :\Iakken. 1971. May 1974) and 70-95 percent in 14 days (9-13 mm)( Dragesund and Nakken, 1973). The delay of a high x mortality period (98 percent in 8 days) to a size range of 15-18 mm in Pacific 10. x herring postlarvae in Japanese waters (lizuka, 1966) may be attributable to x ...-' their retention in a bay. The relatively t- o constant survival rate of yolk-sac and t- ... postlarval Atlantic herring in the Gulf of 0 1.0 X Maine (Graham et aI., 1972 as modified by Cushing, 1974) suggests that observation of high mortality in other populations of herring may result from
XNA ·P-AS offshore drift or errors caused by net avoidance. Offshore drift as a major 0.1 -+--r--,--,----r--,--,--,.--r---.--,-- cause of death was postulated for Pacific o 6 8 10 12 14 16 16 20 LENGTH (mm) herring in British Columbia (Stevenson. Figure 5.-Partial larval survival curves of 1962) although the extent of mortality at Adriatic Sea pilchard (P-AS) and northern sea was not determined. anchovy (NA) in terms of percent of total larvae Observations representing catastroph VS length. See Table 2 for sources. ic mortality may be confused with critical periods. Catastrophic mortality in the early larval stages of herring was documented by Soleim (1942). Marr (1956) and May (1974) suggested that the net in this study was contaminated with herring larvae of previous hauls. Wiborg (1976) and Nikolskii (1969) cited freshwater species (26-33 percent) than in and 2 indicate that mortality is greatest in evidence that such mass mortalities result the 10 examples of marine species (0.01 the postlarval stages of the marine species from storms. 31. 9 percent, mean 4.09 percent). This and also in the Hudson River striped The occurrence of a critical period in may be attributable to higher daily bass. Therefore, the environmental Adriatic pilchard (Karlovac, 1967; May, survival rates and shorter postlarval conditions existing during the relatively 1974) is not strongly supported by periods (22-31 days). An intermediate long postlarval periods may be more Karlovac's data. Samples were collected rate of survival is apparent for the 41-75 critical to the determination of year-class at monthly intervals during the spawning day postlarval periods in the striped bass. 'strength than the egg and yolk-sac larva seasons, and larval densities were environments. tabulated by size. A plot of larval Observations on Possible Critical periods have been postulated numbers as percent of total larvae VS Critical Periods for many species. Larval survival curves, lengths (Fig. 5) following the procedure Enormous fecundities of fishes are presented as percent of larvae VS length, of Lenarz (1972), does not provide any balanced by high mortality rates. The for Pacific hake, jack mackerel, Pacific evidence ofa critical period. However. no occurrence of most mortality during a sardine, and northern anchovy (Lenarz, correction for variation in growth rate short period in early development is the 1973) revealed some evidence for early was made. critical period concept. Total losses are critical periods, but there was also some Data on striped bass of the Potomac undoubtedly highest during egg or yolk degree of extrusion through the 0.55-mm River, Chesapeake and Delaware Canal, sac larva stages (Farris, 1960, Dekhnik mesh net. Survival curves of pacific and Hudson River (Table I, Fig. 3) reveal et aI., 1970). If a critical period can be sardine (Fig. 2) and northern anchovy very high mortality of eggs (90-99.7 identified, then it is likely that the larvae (Fig. 5) did not provide any percent). Highest egg mortality of consequences of human perturbations evidence of a critical period when Potomac River striped bass is apparent would be much greater if they occurred densities were corrected for loss of small when egg production is based on after the critical period rather than larvae through the mesh (Lenarz, 1972). fecundity-at-age data. The marked before. Survival curves of herring larvae do differences in the striped bass survival Critical period may also be viewed in not follow a consistent pattern (Fig. 2,4). curves for the three study areas are terms of relative survival rates among the Mortality rates of Norwegian herring influenced by the use of hypothetical developmental stages. Data in Tables I larvae were estimated at 94 percent in 6 survival rates for the Chesapeake and
8 Marine Fisherie.\ Re\'ie\\' 1.0 to larva survival. Other models require additional data on survival rates of larvae NP YP ~H and juveniles, population size, larval • • '*PL 0.9 w-J; X production, compensatory reserve, etc. ~ • X Such information is available for a very JM > limited number of species and must be "a o.a X used cautiously in predictive modeling. ...a: X Q. Data collected at one site may not be ~ .eM applicable to another if there are -:: 0.7 differences in natural factors, such as substrate characteristics, disease, water
0.6 level, dissolved oxygen, water temperature. wave action, predation, cannibalism, food supply, carrying capacity. and condition of spawners 10 20 30 40 50 60 70 60 90 100 liD 120 130 Interaction of more than one stress has TOTAL DAYS OF DEVELOPMENT been frequently observed It has been Figure 6. Relationship of daily survival roles anu length, of pruposed that low water temperatures developmental period in striped ba" (X), chub lll J111rc!1 /97') for predation which resulted in 15-40 models for entrainment of striped bass in mortalities in Clyde herring eggs. In A. percent mortality in one herring study the Hudson River yielded conflicting Saville (editor). Symposium on the biology of early stages and recruitment mechanisms (Dragesund and Nakken, 1973). The results. Major differences in predictions of herring. p. 27-29. Rapp. P-V. Reun Cons. ratio of swim-up larvae and deposited were related to definition of life stages, Perm. Int. Explor. Mer. 160. eggs does not provide a reliable measure whether fishing mortality and mortality Bjorn, T. C. 1966. Salmon and steelhead in of egg survival because mortality during of larvae and juveniles were density vestigations. Idaho Fish Game Dep., Proj. F-49-R-4, Job 3, 183 p. the period of hatching and recruitment dependent or density-independent, Brasch, J. 1949. Notes on natural reproduction into the plankton may be high (Forney, method of computing recruitment of of the eastern brook trout (Sa!l'Idinll.1 1968; Dragesund and Nakken, 1973). young-of-the-year fish, and major lominali.I) with a preliminary report of sev Furthermore, the youngest yolk-sac differences in values of parameters such eral experimcnts on the subject. Wis. Con serv Dep.. Invest. Rep. 653, 9 p. larvae often associate with the bottom as egg production, population size, and Braum, E. 1971. The egg and larval phase. In and are not fully vulnerable to plankton survival probabilities (Swartzman et a!., W. E. Ricker (editor), Methods for assess sampling gear in freshwaters. Mortality 1977). ment of fish production in fresh waters, of pelagic eggs has been determined from p. 179-198. IBP Handb. 3. Blackwell Sci. ratios of various egg stages, but this is Publ., Oxford. Acknowledgments Breder, C. M.. Jr., and D. E. Rosen. 1966. tenuous when of short duration such as I Modes of reproduction in fishes. Nat. Hist. or 2 days. Polgar (1977) indicated that Compilation of fish egg and larval Press, Garden City, N.Y., 941 p. Briggs, J. C. 1953. The behavior and reproduc striped bass eggs were not adequately survival data has heen encouraged by sampled during the daytime because this tion of ,almonid fishes in a small coastal s.c. Marcy, Jr. and other NUS staff who stream. Calif Dep. Fish Game, Fish. Bull., species spawns at night. The were concerned with power plant impact 94, 62 p. semibuoyant nature of the eggs may also studies, under the direction of P. V. Busch, W.-D. N., R. I.. Scholl, and W. L. Hartman. 1975. Environmental factors af result in low estimates when sampled Morgan, Vice President and General with plankton gear. Selection of fecting the strength of walleye Manager of Ecological Sciences ,(Stizostedion vitreum vitreum) year-class in representative egg survival values is Division. I thank W. J. B. Johnson for western Lake Erie, 1960-70. J. Fish. Res. particularly important in the equivalent drafting the figures. Critical reviews were Board Can. 32: 1733- 1743. Ciechomski, J D. de, and D. A. Capezzani. adults model because of the proportional provided by B. C. Marcy and E. P. inverse relationship with the projected 1973. Studies on the evaluation of the Wilkins of NUS Corporation and by S. spawning stocks of the Argentinean anchovy, adult loss. Because of the sampling Gregory and J. Andreasen of the U.S. (EnKraulis anchoi/{J), on the basis ofegg sur problems and natural variability, Fish and Wildlife Service. veys. In B. B. Parrish (editor), Fish stocks application ofa possible range ofsurvival and recruitment, p. 293-301. Rapp. P.-V. values is recommended. Reun. Cons. Perm. Int. Explor. Mer 164. Literature Cited Clady, M. D. 1975. Early survival and recruit Yolk ·sac larvae are the most difficult ment "of smallmouth bass in northern of the three developmental stages to Michigan. J. Wildl. Manage. 39: 194-200. sample because they are frequently Ahlstrom, E. H. 1954. Distribution and abun 1976. InOuence of temperature dance of egg and larval populations of the and wind on the survival of ea rly stages of extruded through the net in marine Pacific sardine. U.S. Fish Wildl. Serv., Fish. yellow perch, Perca/lavescens. J. Fish. Res. studies and are in a transition between a Bull. 56:83 -140. Board Can. 33: I 887-1893. demersal and pelagic existence in most Allen, K. R. 1951. The Horokiwi Stream. A Cloren, J. E. 1976. The survival ofcoho salmon freshwater species. Thus, survival of study ofa trout population. N. Z. Mar. Dep., (Oncurhvnchus kisU/ch) eggs in two Fish. Bull. 10, 238 p. Wisconsin tributaries of Lakc Michigan. yolk-sac larvae is generally based on Allan, R. c., and J. Romero. 1975. Underwater Am. MidI. Nat. 96:451-461. survival curves which exclude data for observations of largemouth bass spawning Coble, D. W. 1961. InOuence of water ex the smallest larvae or have incorporated and survival in Lake Mead. In R. H. Stroud change and dissolved oxygen in redds on sur vival of steelhead trout embryos. Trans. Am. correction factors (Lenarz, 1972). Earlier and H. Clepper (editors), Black bass biology and ma nagement, p 104- I 12. Sport Fishing Fish. Soc. 90:469-474. observations of possible critical periods Colton, J. B. Jr. 1959. A field observation of Institute, Wash., D.C. mortality of marine fish larvae due to warm in marine fishes generally reflect this Bailey, R. M, J. E. fitch, E. S. Herald, ing. Limno!. Oceanogr. 4:219:222. E. A. Lachner, C. CI 'ndsey, C. R. Robins, sampling error. Such data gaps do not Cushing, D. H. 1974. The possible density and W. B. Scott. 1970. A list of common and preclude impact modeling and may dependence of larval mortality and ad ult ,cientific names of fishes from the United represent a minor factor in relation to the mortality in fishes. In J. H. S. Blaxter (edit States and C"nada. 3d ed Am. Fish Soc, or), The early life history of fish, p. 103-111. various assumptions that are required Spec. Publ. 149 p o. Springer-Verlag, N. Y. and the minimal information available Ball, O. P., and O. B. Cope 1961. Mortality Dekhnik, T V 1960. Mortality codficients on compensatory reserve in fishes. studies on cuttroat trout in Yellowstone during two embryonic and larval devdop Lake U. S. Fish Wildl. Serv., Res. Rep. 55, Development of survival data is men" of the !llack Sea anchovy Tr 62 p. lagging far behind the modeling state-of Sevastop BioI. Stn. 1m. A.D KO\alenskogo Bannister, R. C. A., D. Harding, and S. J. Akad "auk Ukr. SSR 13:210-244 the-art in impact assessment. As a result, Lockwood. 1974. Larval mortality and sub ____ . 1963. Patterns of variation in important decisions are being made sequent year-class strength in the plaice abundance and mortality of Engraulis (Pleuronectes plateua L). In J. H. S. from incomplete data. A need for further l'lIcra.lic!J,,!w {)()/Ilicl/.l Alex eggs and larvae Blaxter (editor), 1 he parly life history offish, in the Black Sea Tr. Sevastop. BioI. Stn. 1m. evaluation of models is also evident in the p. 21 ·37. Springer-Verlag, N.Y. A D. Kovalenskogo Akad :'-Jauk LJkr SS R literature. As an example, a series of Baxter, I. G. 1971. Devel0pmentaJ rates and 16:340-35i( 10 Marine Fisheries Review 1964. Changes in the ahundance Hanavan. M.·G.. and B. E. Skud 1954. Inter Lake Winnibigoshish. Minnesota. and con of Black Sea mackerel eggs and larvae dur tidal spawning of pink salmon Fish Bull.. necting waters. Trans. Am. Fish. Soc. 90: ing the development period. Tr Sevastop. U.S. 56(95): 166- I85 312-322. BioI. Stn. 1m. A. D. Kovalenskogo Nauk Hanson. C. H.. J. R. White. and H. W. l.i. 1977 Johnson. W. E. 1965. On mechanisms of self Ukr. SSR 15:292-JOI. Entrapment and impingement of fishes by regulation of population abundance in ____. 1970. Food supply and thc causes power plant cooling-water intakes: An over Oncorhl'l1chus nerka. Mitt. lnt. Ver. of mortality among the larve of some com view. Mar. Fish. Rev. J9( 10):7-/7 Limnol. 13:66-87. mon Black Sea fishes. Probl. Ichthyol. 10: Hartman. W. L.. C. W. Strickland. and D. T Jones. R.. and W. B. Hall. 1974. Someobserva J04-J 10. Hoopes. 1962. Survival and behavior of tions on the population dynamics of the lar Dragesund. 0 .. and O. Nakken. 1971 Mortal sockeye salmon fry migrating into Brooks val stage in the common gadoids. In J. H. S. ity of herring during the early larval stage in Lake. Alaska. Trans. Am. !-ish. Soc. 91'1 JJ Blaxter (editor), The early life history offish. 1967 111 A. Saville (editor). Symposium on I J9. p. 87-102 Springer-Verlag. N.Y the biology of early stages and recruitment Hassler. T. J. 1970. Environmental influences Karlovac. J. 1967. Etude de I'ecologie de la mechanisms of herring. p. 142-146. Rapp. on early development and year-class sardine. Sardina pilchardus Walb., dans la P.-V. Reun. Cons. Perm. Int. Explor Mer strength of northern pike in Lakes Oahe and phase planctonique de sa vie en Ad riatiq ue 160. Sharpe. South Dakota. Trans. Am. Fish. moyenne. Acta Adriat. 13(2). 109 p. ____ , and 197J. Relation- Soc. 99:369-375 Koski. K. V. 1966. The survival ofcohosaimon ship of parent stock si/e and year cia" Hausle. D. A., and D. W Coble. 1976. Influ (Oncurhrnchlls kisUlch) from egg deposition strength in Norwegian spring spawning her ence of sand in redds on survival and emerg to emergence in three Oregon coastal ring. 111 B. B. Parrish (editor). !-ish stocks ence of brook trout (Sall'elinus jiJl1linali.\). streams. M. S. Thesis, Oregon State Univ.. and recruitment. p. 15-29. Rapp. P.-V. Trans. Am. Fish. Soc. 105:57-63. Corvallis. 84 p. Reun. Cons. Perm. Int. Explor. Mer 164. Kramer. R. H., and L. L. Smith. Jr 1962. For Hayasi. S. 1967. A note on the biology and fish Edsall, J. A. 1975. Electric power generation mation of year classes in largemouth bass. ery of the Japanese anchovy Engraulis and its influence on Great Lakes fish. /n Proc. Trans. Am. Fish. Soc. 91 :29-41. japonica (Houttuyn). Calif. Coop. Oceanic Second ICMSE Conference on the Great Fish. Invest. Rep. 11 :44-57. ____. and 1965. Effects of Lakes. p. 453-462. Argonne Nat. Lab.. Hempe I. G. 1971. Egg prod uct ion a nd egg mor suspended wood fiber on brown and rain Argonne. III. tality in herring. /n A. Saville (editor). Sym bow trout eggs and alevins. Trans. Am. Fish. Farris. D. A. 1960. The effect of th ree different posium on the biology of early stages and re Soc. 94:252-258. types of growth curves on estimates of larval cruitment mechanisms of herring. p. 8-11. Krogius, F. V. 1951. [Behavior of the numbers fish survival. J. Cons. Perm. Int. Explor. Rapp. P.-V. Reun. Cons. Perm. Int. Explor. of Oncorh..nchlls lIerka Walb.] [In Russ.] Mer 25:294-306. Mer 160. Izv. Tikhookean Navchno-Issled. Inst. ____.1961. Abundance and distribution of Hess. K. W.. M. P. Sissenwine.and S. B. Saila. Rybn. Khoz. Okeanogr. 35:3-16. eggs and larve and survival of larvae ofjack 1975. Simulating the impact of the entrain Larkin. P. A. 1977 Pacific salmon. In J. A. mackerel (Trachurus srml17elricus). Fish. ment of winter flounder larvae. In S. B. Saila Gulland. (editor). Fish population dynam Bull., U.S. 61:247-279. (editor). Fisheries and energy production: A ics. p. 156-186. John Wiley & Sons, N.Y. Forney. J. L. 1968. Production ofyoung north symposium. p. 1-30. D. C. Heath and Co.. Latta. W. C. 1963. The life historyofthesmaJl ern pike in a regulated marsh. N. Y. Fish Lexington, Mass. mouth bass. Microplerus d. dolomieui. at Game J. 15:143-154. Hjort. J. 1914. Fluctuations in the great fish Waugoshance Point. Lake Michigan. Mich. ____. 1976. Year-class formation in the Dep. Conserv.. Inst. Fish. Res. Bull. 5. 56 p. walleye (SIi=!Jsledion I'ilrewn \,ilreul17) pop eries of northern Europe viewed in the light of biological research. Rapp. P.-V. Reun. 1975. Dynamics of bass in large nat ulation of Oneida Lake, New York. 1966-73. Cons. Perm. Int. Explor. Mer 20: 1-228. ural lakes. In R. H. Stroud and H. Clepper J. Fish. Res. Board Can. 33:783-792. Hobbs. D. F. 1940. Natural reproduction of (editors). Black bass biology and manage Franklin. D. R.. and L. L. Smith, Jr. 1963. Ear trout in New Zealand and its relation to den ment. p. 175-182. "port fish. Inst. Wash.. D.C. ly life history of the northern pike. ElOx sity of populations. N.Z. Mar. Dep.. Fish. Lenarz. W. H. 1972. Mesh retention of larvae lucius L.. with special reference to the factors Bull. 8.93 p. of Sardinol'.\· meruleaand Engraulis mordax influencing the numerical strength of year by plankton nets. Fish. Bull .. U.S. 70:839-848. classes. Trans. Am. Fish. Soc. 92:91-110. Horst, T. J. 1975. The assessment of impact Galkina. L. A. 1971 Survival of spawn of the due to entrainment of ichthyoplankton. /11 ____. 1973. Dependence ofcatch rates on Pacific herring (Clul'ea harengus pallasii S. B. Saila (editor). Fisheries and energy pro size of fish larvae. /11 B. B. Parrish (editor). Val.) related to the abundance of the spawn duction: A symposium. p. 107-118. D. C. Fish stocks and recruitment. p. 270-275. ing stock. In A. Saville (editor). Symposium Heath and Co.. Lexington, Mass. Rapp. P.-V. Reun. Cons. Perm. Int. Explor. on the biology of early stages and recruit Houde. E. D. 1977a. Abundance and potential Mer 164. ment mechanisms of herring. p. 30-33. Rapp. yield of the round herring. Etrul17eus leres. LMS (Lawler. Matusky & Skelly Engineers). P.-V. R€un. Cons. Perm. Int. Explor. Mer and aspects of its early life history in the east 1975. Report on development ofa real-time. 160. ern Gulf of Mexico. Fish. Bull.. U.S. 75:61-89. two-dimensional model of the Hudson River Gj,0'saeter, J., and R. Saetre. 1974. The use of ____ . 1977b. Abundance and potential striped bass population. LMS Proj. No. 115 data on eggs and larvae for estimating yield of the Atlantic thread herring, 149, 71 p. spawning stock of fish populations with de Opislhonema oglinum, and aspects of its Marr, J. C. 1956. The "critical period" of the mersal eggs. InJ. H. S. Blaxter (editor). The early life history in the eastern Gulf of early life history of marine fishes. J. Cons. early life history of fish. p. 139-149. Mexico. Fish. Bull., U.S. 75:493-512. Perm. Int. Explor. Mer 21: 160-170. Springer-Verlag. N. Y. ____ .I 977c. Abundance and potential May. R. C. 1974. Larval mortality in marine Graham. J. J.. S. B. Chenoweth. and C. W. yield of the scoled sardine. Harenglll" fishes and the critical period concept. In J. Davis. 1972. Abundance. distribution. jaguana, and aspects of its early life history H. Blaxter (editor), The early life history of movements. and lengths of larval herring in the eastern Gulf of Mexico. Fish. Bull.. fish. p. 3-19. Springer-Verlag. N. Y. along the western coast of the Gulfof Maine. U.S. 75:61J-628. McFadden. J. T. 1977. An argument support Fish. Bull .. U.S. 70:307-321 lizuka. A. 1966. Studies on the early life history ing the reality of compensation in fish popu Grauman. G. B. 1973. Investigations of factors of herring (Clupea pallasi C. et. V.) in lations and a plea to let them exercise it. /n influencing fluctuations in abundance of Akkeshi Bay and Lake Akkeshi, Hokkaido. W. Van Winkle (editor). Proceedings of the Baltic Cod. In B. B. Parrish (editor). Fish [In Jpn.. Engl. summ.] Bull. Hokkaido Reg. conference on assessing the effects of power stocks and recruitment. p. 73-76. Rapp. Fish. Res. Lab. 31:18-63. plant-induced mortality on fish populations. P.-V. Reun. Cons. Perm. Int. Explor Mer Johnson. F. H. 1961. WaJleyeeggsurvivaldur p. 153-183. Pergamon Press. '. Y. 164. ing incubation on several types of bottom in McKenzie. R. A. 1947. The effect of crowding March /979 " of s'1'elt eggs on the production of larvae. In W Van Winkle (editor) Proceedings of Explor Mer 164. Fish. Res Board ("n., Atl Coasl Stn Prng. the conference on assessing the effects of Soin. S G. 1971 Ecological and morphologic Rep. 39'11-13. power-plant-induced mortality on fish pop al peculiarities of the development of two Mc"leil. W. .1.1966 Effectofthespa'vningbed ulations, p. 110-126. Pergamon Pless, "I.Y forms of White Sea herring (Clupea environment on reprNjuction 'If pink and Portner. E. M. 1975. Testimony on striped hass haren/?us maris-alha Berg.) In A. Saville (cd chum salmon Fish. B'JII.. S (,5:49~ 523 entrainment by Summit Power Station itor). Symposium on the biology of early Moring. .I R.. and R. I.. I ant7. 197.5. The Testimony before the Atomic Safety and Li stages and recruitment mechanisms of her Alsea ,vatershed study Effects of loggin!! on censing Board in the mailer of '>ummit ring. p. 42-45. Rapp. P.-V. Reun. Cons. Ihe a /2 Marine Fisheries Re"iew