CalCOFI Reports, Vol. 11, 1967 - California Cooperative Oceanic ...

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32 CALIFORNIA COOPERATIVE OCEANIC FISHERIES INVESTIGATIONSof temperature than the animal actually experiences.One conspicuous example of how misleading such asimple diagram might be is found in the Mediterranean.Summer surface temperatures are from 22' to28°C and winter values are from about 10°C to17°C. There is no overlap. On the other hand, weknow that these very high surface temperatures insummer are restricted to the upper few meters, andthat by being as little as 15 m beneath the surface thefish might easily find temperatures less than 22°Ceverywhere, even in August. This may apply in manyof the other areas as well in summer, so that theupper limit of surface water temperature may notrepresent the temperature the fishes experience. Likewise,Dr. Hayasi reports, the fish avoid the extremelylow water temperatures of the northern Sea of Japanin winter by staying in the southern area, which ismuch warmer. On the other hand, in some areas thewinter temperatures are inescapable. Fishes in theBlack Sea in winter must undergo temperatures ofabout 8°C: there is no warmer water anywhere inthe Black Sea at that time.On Figures 2 and 3 these open-ocean ranges ofsurface temperature in winter and summer are shownas rectangles with temperature as the vertical scaleand salinity as the horizontal scale. In both cases theentire range of oceanic values of temperature andsalinity is shown in order to emphasize the proportionof these ranges that Engraulis occupies. All exceptone of the species are included on Figure 2 : E, encrasiclzolzis'range is much wider and is shown separatelyon Figure 3.Figure 2 would seen1 to indicate that the oceanichabitat of Engraulis comprises almost the entire rangeof temperature in the ocean but only a small part ofthe salinity range. This would be a very wrong inferenceindeed. Baxter (p. <strong>11</strong>0) and others have shownthat Engradis retreats to offshore and deeper waterto avoid some extremes of temperatures; the totalrange, which includes extreme summer surface temperaturesthat the fishes may avoid by a slight submergence,and the extreme winter temperatures in thenorthern part of the Sea of Japan that the fish mayavoid by moving a short distance to the south, may bequite misleading. On the other hand, it has also beenshown that the fish do move into the quite brackishwaters of bays and estuaries when the temperature isnot too extreme. Therefore, all of these rectanglesshould extend an uncertain distance to the left on thegraph to include, at least during some part of theyear, waters of very low salinity indeed. This is emphasizedin Figure 3 by the ranges of E. encrasicholus.The open-ocean values from the North Sea southwardpast Spain to western North Africa look very muchlike the ranges on Figure 2 of the other Engraulisspecies. But the ranges in the Baltic, the Mediterranean,the Black Sea and the Sea of Azov emphasize thereal capability of encrasicholns to endure almost-freshas well as extremely saline water and very cold water.It is apparently the seasonal change in temperaturethat causes them to leave the Baltic, North and Azovseas, since the salinity does not change very much withseason.Looking again at Figure 2, some of the open-oceansalinity ranges appear to be very narrow. This signifiesthat the total range of offshore salinity values inthe Engraulis habitat is small, not that Engraulis islimited to a narrow range of salinity, since we knowthat it occurs in brackish waters. It appears thatEngradis can endure the total range of salinity encounteredin the open sea, including the Mediterraneanvalues above 39p/o0, but may be limited toonly part of the temperature range. Various investigatorswho are better informed may correct me, butit seems possible that Engraulis may actually notexperience temperatures much below 7 or 8"C, thoughit may experience these in many areas besides theBlack Sea. Resident populations of E. mordax nearVancouver Island will experience 7 or 8" in winterand if E. anchoitn and E. enchrasicholzis do notretreat completely from the Falkland Current andNorth Sea areas some of the individuals will undergovalues of about 8°C or less.In winter E. encrasicholzcs is found only at temperaturesless than 18" and it may by a slight submergencein summer avoid temperatures more than 22°C.Blackburn (this symposium) has shown that E.australis occurs only between about 10°C and 20"C,and Ahlstrom (1956) has said that most of the eggsand larvae of E. rnordax have been taken in aboutthat range, though some have been taken at more than23°C. The total range of the area occupied by E.ringens is from about 10°C to 23"C, and this includesnorth to south and winter and summer : slightmigrations might reduce this appreciably.E. japonicus capensis simply has no opportunity toendure cold water: about 15°C is the lowest surfacetemperature he may encounter at the tip of Africa,which is only about lat. 35"s. Likewise, a populationof E. encrasicholus that remains in the Mediterraneanmay not find water colder than 10°C at any timeof year.CONDITIONS LIMITING ENGRAULISWe may speculate, then, that Engradis is notlimited by the salinity values encountered in theocean or in estuaries: it not only occurs but spawnsin regions of very low as well as very high salinity.We may speculate also, at least until the other speakerscorrect me, that Engraulis is limited by temperature,since it does not appear in either the coldest orthe warmest oceanic conditions. Perhaps a range from6°C to 22 or 23°C would include all, or nearly all,of its actual occurrences. This would account for itslimited latitudinal range and for its most strikingmigrations from the Baltic, North, and Azov seas,whereas salinity variations would not.This really does not add very much to what most ofyou know already, and it does not by any meansspecify the habitat of Engraulis. By this I mean to saythat there is a vast area of ocean with surface temperaturebetween 6°C and 22°C-about $ of the worldocean, in fact-but that Engraulis inhabits, so far aswe know, less than l/lo of this area. Therefore temperaturealone cannot define the habitat of Engraulis.
REPORTS VOLUME XI, 1 JULY 1963 TO 30 JUNE 1966 33What are some of the other quantities that mightbe important to Engraulis, and that might explaintheir absence from other areas that seem to have theproper temperature and salinity ?First, it appears to be a coastal genus. Such informationas I have got so far indicates that althougheggs and larvae are sometimes found some hundredsof miles offshore they are definitely tied to a coastalpopulation-that is, they do not appear in areasseparated from the coast. I do not know how to interpretthis. I have consulted several biologists andhave concluded that there is no single, generallyaccepted explanation as to what there is about coaststhat appeals to some nekton.It is true that most coastat regions are somewhatmore productive than the offshore temperate-zoneareas, but the genus can inhabit the Mediterranean,where productivity is fairly low. The region nearthe equator and at some distance west of South Americafits the temperature requirements of Efigraulisand is extremely productive, yet Elzgraulis does notappear to be found any great distance offshore there.Likewise there are other offshore temperate-zone areasof relatively high productivity such as the regionaround lat. 45"N in the Pacific that Engraulis doesnot inhabit. Therefore temperature and productivityare not enough for Engraulis: there has to be a coastnearby-perhaps some place where the bays, lagoonsor estuaries or the inshore countercurrents and tur-bulence may provide a firm foothold for a population,so that it is not swept entirely away by the prevailingcurrents, as it might be in the truly pelagic areas.Having accepted coasts and a particular temperaturerange as requirements for Engraulis, whetherwe can explain the relation or not, we have eliminatedmost of the ocean as habitable areas for Engraulis.We find that what is left, that is, coastal waters withtemperature ranges between about 6" and 22"C,is in fact inhabited by Engraulis except for one conspicuousomission : the eastern coast of North America.In August the temperature range from 6" to 22°Cis found between Labrador and New York, in Februarybetween New York and Cape Hatteras. Thearea of overlap is small but so is it in some of the otherhabitats: a minor amount of seasonal migration couldkeep Engraulis at optimum temperatures throughoutthe year in this general region. If inshore habitatsare required this coast has plenty of estuaries andsounds that would seem to compare favorably withthose of the other coastal areas inhabited by Elzgraulis;I cannot offer any speculation as to 'dhyEngraulis does not inhabit this area.REFERENCESAhlstrom, E. H. 1956. Eggs and larvae of anchovy, jack m&-erel, and Pacific mackerel. Calif. Coop. <strong>Oceanic</strong> Fish. Inmpt.,Prog. Rept., 1 April, 1955 to 30 June, 1956, :33-42.2-9 5 7 5 7
Page 1 and 2: STATE OF CALIFORNIAMARINE RESEARCH
Page 3 and 4: STATE OF CALIFORNIADEPARTMENT OF FI
Page 5 and 6: RONALD REAGAXGovcriwr of the Slate
Page 7 and 8: PART 1REVIEW OF ACTIVITIESJuly 1,19
Page 9 and 10: REPORTS YOLUAIE SI, 1 JULY 1963 TO
Page 11 and 12: REPORTS VOLUNE XI, 1 JULY 1963 TO 3
Page 13 and 14: REPORTS YOLUME SI, 1 JULY 1963 TO 3
Page 15 and 16: REPORTS VOLUME XI, 1 JULY 1963 TO 3
Page 17 and 18: REPORTS vor,uiwIi; SI, 1 JULY 1063
Page 19 and 20: REPORTS TOT2T71\IF: SI, 1 JUJIT 196
Page 21 and 22: IiEPOHTS TOLUME XI, 1 JULY 1963 TO
Page 23 and 24: REVIEW OF THE PELAGIC WET FISHERIES
Page 25 and 26: KEI'OiiTH TOLUJIE SI, 1 JULY 1963 T
Page 29 and 30: PART IISYMPOSIUM ON ANCHOVIES, GENU
Page 31 and 32: OCEANIC ENVIRONMENTS OF THE GENUS E
Page 33: KEI'OKTS VOLIXI.: SI, 1 JULY 1963 T
Page 41 and 42: ~~~REPORTS VOLUME XI, 1 JULY 1963 T
Page 45 and 46: REPORTS VOLUME SI, 1 JULY 1963 TO 3
Page 47 and 48: 130'E 132' 134' 136' 138' 140' 142-
Page 49 and 50: REPORTS VOLUSIE SI, 1 JULY 1963 TO
Page 57 and 58: KI3I’ORTH VOLUJIE XI, 1 JULY 1963
Page 61 and 62: REPORTS VOLUME SI, 1 JULY 1963 TO 3
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Page 67 and 68: REPORTS T’OLUME XI, 1 JULY 1963 T
Page 69 and 70: INFLUENCE OF SOME ENVIRONMENTAL FAC
Page 71 and 72: REPORTS Y‘OLUJIE XI, 1 JULY 1963
Page 75 and 76: ~table shows the values calculated
Page 77 and 78: ateREPORTS T-OLTJIT", SI, 1 JULl 19
Page 79 and 80: REPORTS POLGNE SI, 1 JU LY 1963 TO
Page 81 and 82: REPORTS VOLUXE XI, 1 JULY 1963 TO 3
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_________--_____REPORTS VOLUJIE SI,
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REPORTS TOLTIJIE SI, 1 JULY 1963 TO
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-20/5-0 10-f 5-w 25-0 20-= 15-: 10-
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REPORTS VOLUNE SI. 1 JULY 19G3 TO 3
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REPORTS VOLUME XI, 1 JULY 1963 TO 3
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REPORTS VOLURlE SI, 1 JULY 1963 TO
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THE PREDATION OF GUANO BIRDS ON THE
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iod and after 8 AM during the rest
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FISH E RYThe California anchovy fis
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~~ ::REPORTS VOLUME XI, 1 JULY 1963
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CO-OCCURRENCES OF SARDINE AND ANCHO
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120 CALIFORNIA COOPERATIVE OCEANIC
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CALIFORNIA COOPERATIVE OCEANlC FISH
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126CALIFORNIB COOPERATIVE OCEANIC F
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~~ ~130 CALIFORNIA COOPERATIVE OCEA
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132 CALIF0RhTTIA COOPERATIVE OCEANI
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THE ACCUMULATION OF FISH DEBRIS IN
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PART IllSCIENTIFIC CONTRIBUTIONS
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REPORTS VOLUME SI, 1 JULY 1963 TO 3
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REPORTS VOLU&IE XI, 1 JULY 1963 TO
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SUMMARY OF THERMAL CONDITIONS AND P
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SEASONAL VARIATION OF TEMPERATURE A
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including the semiannual harmonic?
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REPORTS VOiLUME XI, 1 JULY 1983 TO
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170 CALIFORNIA COOPERATIVE OCWIC FI
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172 CALIFORNIA COOPERATIVE OCBANIC
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184CALIFORNIA COOPERATIVE OCEANIC F
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CONTENTSI. Review of Activities Pag
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