W&M ScholarWorks Dissertations, Theses, and Masters Projects Theses, Dissertations, & Master Projects 1958 A Comparative Study of Meristic Variation in the American Eel (Anguilla rostrata) and Atlantic Anchovy (Anchoa mitchilli) Ernest C. Ladd College of William and Mary - Virginia Institute of Marine Science Follow this and additional works at: https://scholarworks.wm.edu/etd Part of the Fresh Water Studies Commons, Morphology Commons, Oceanography Commons, and the Zoology Commons Recommended Citation Ladd, Ernest C., "A Comparative Study of Meristic Variation in the American Eel (Anguilla rostrata) and Atlantic Anchovy (Anchoa mitchilli)" (1958). Dissertations, Theses, and Masters Projects. Paper 1539617372. https://dx.doi.org/doi:10.25773/v5-dd73-y349 This Thesis is brought to you for free and open access by the Theses, Dissertations, & Master Projects at W&M ScholarWorks. It has been accepted for inclusion in Dissertations, Theses, and Masters Projects by an authorized administrator of W&M ScholarWorks. For more information, please contact [email protected]. A COMPARATIVE STUDY OF MERISTIC VARIATION IN THE AMERICAN EEL (ANGUILLA ROSTRATA) AND ATLANTIC ANCHOVY (ANCHOA MITCHILLI) by Ernest Cooiidge Ladd A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS JJ KUM. TtiiS COLLEGE OF WILLIAM AND MARY 1958 £> TABLE OF CONTENTS * C « Rays. * . 9 - * « Sublect Page ** ^ *. i - > a *• * * * « . * « « . *. / « ' * 9 ♦ -5 INTRODUCTION. .................... ......... 1 *. / *- u ; u ' W r - ''■•:• ■'*£ Economic Importance of Eel and Anchovy . 1 ~t>i t - History and Purpose of Her Is tic Studies. 2 Purpose of Present Investigation ..... 4 Heristic Variation in the American Eel . • • • • • © • ‘5 Meristic Variation in the Atlantic Anchovy •■ a-, a • • • • 6 MATERIALS AND METHODS ............. 7 &: STATISTICAL ANALYSES. .' . vjf. .rv .if.?id. y- 1% I • * • • • » 8 . ., -. tr vi ■, * *. ■ *. & « * i * <*? *. ■** * w > * - s * 7 THE AMERICAN EEL. .... .... 1 • t # 10 r. •' - « • * < - - * » -V ■ v » v « * - * ■* . * to **- r .{ i £ Numbers of Vertebrae . • • * • • * • 10 ■ f y *‘, V' -'if“» b . ,iaD. r- • «.-»'**' * » V V »• « * * to . ■£* > « '* « a- ■ ■ .* ■ i Variation in Vertebral Counts with Length. • • • • • • • 10 — Precaudal and Caudal Vertebrae . ♦ . « « « • • * a 11 Structural Variations.............. .. •# • • • • • ♦ 12 > Numbers of Fin Rays. * • • • • • * 14 Relationship Between Numbers of Body Segments and Fin Rays • • . • . 15 THE ATLANTIC ANCHOVY. .......... ............. 15 Numbers of Vertebrae • • • * • • • 15 Variation in Vertebral Counts with Length. ♦ • ♦ • • .' • 16 Precaudal and Caudal Vertebrae ...... • • a • • f •16 Structural Variations. • • 17 Numbers of Fin Rays. .................... 18 Dorsal Fin Rays . , . ..................... 18 mrr Z5£e Anal Fin Rays. ............... 18 Pectoral Fin Rays. ........... 19 Relationship Between Numbers of Body Segments * ' vm* r,." > 4 and Fin Rays ........... „ .... 19 COMPARISON OF MERISTIC VARIATION IN EEL AND ANCHOVY. ...... 20 K-; .} i „ w ■: » •'< * «* » Numbeis of Vertebrae ..................................... 20 1 *’ * ... *J - * ‘■J *. f . t‘, . I ,. '■- *-e ' \ ? y Variation in Vertebral Counts with Length. .....••• 21 H ■’ ,. ■' , ... * n - *••; ii;i v, Ci^/i Structural Variations............... 21 v ■ , v..- - • ...* ..*.■?•■ x , i* Numbers of Fin Rays. • • . ...... 22 Relationship Between Numbers of Body Segments and Fin Rays .................... 23 SUMMARY . .... ......... .... .. 24 LITERATURE CITED. * « . » «. > « . « . • . -■» . * 26 * *' ift .»;■> t « t * ■:-> C < .■ -s1 \ ? A l t. •. "5. *• J 4 > -■* . ‘i’v-'Uj . \'.y -'-.h ‘i. "* ft-1*; r ?*.■'' * L . > i-... U *" .• t ?; •.< • ’ : k’jf. I, : • .. *ii*. "... ■, ;..T. i v v i ’ \ v • . i i 'it. * . i«v ^ V. ^ i i ■- i. - ^ •*. *. r - ■ - ■: ?%.. t <• I: * -a . • • i . i *■«. iv v - L . - ■* ; c v .• t,} •. i-yiA ‘ . tjf <*>t •* * > - ACKNOWLEDGEMENfs .... ... .. j.1 ; „ it in i The writer wishes to express his appreciation to the many people who assisted in this study, :r 7 7 . I : l . -.1 -.--v . 'y The sample of elvers from Nova Scotia was provided by Dr. A. W. H. Needier and the New Hampshire sample by Professor C. Floyd Jackson, Clarence Richards and Maurice Pare. Elvers from Virginia and all anchovies were collected with Mr. William H. Massmann of the Virginia Fisheries Laboratory.'. 7 ... i. ■. * .5 . ■ . I'.-j rivs if.*''.a ,'’°^rCK,v r Special thanks are due to Messrs. H. E. Stevens, B. B. Lineberry and W. W . Cloe of the Statistical Section and M. L. Winkler, Staff Photo­ grapher, of the American Viscose Corporation, Fredericksburg, Virginia. The .typing was done by Mrs. Lois Grigsby, Miss Miriam Richards and Mrs. Edith Briscoe,, and Miss Particia Conner. - ; sry d ‘s. vur- ■- „ r- 1 The writer is grateful to Dr. J. L. McHugh, Director of the Virginia Fisheries Laboratory, for his technical advice and guidance throughout the study. The persistent confidence and help given by Dr. McHugh and the author1s wife, Alice Ladd, are largely responsible for completion of the study. Special thanks are also due Dr. G. W. Low, Jr., Plant Manager, and Dr. C. W. Tasker, Technical Superintendent, of the American Viscose Corporation, Fredericksburg, Virginia, and to the entire staff of the Virginia Fisheries Laboratory for their assistance, under­ standing and encouragement. a . M>i : - '-r i, >.£*..) u-’ -» . * INTRODUCTION : Economic Importance of Eel and Anchovy v \ i r; r „■.. ■. v \ ; ? The eel has long been a food fish of secondary importance in Chesapeake Bay and its tributaries, Hildebrand and Schroeder (1927) re­ ported that in the commercial catch of 1920 it ranked eleventh in qu^ptity and tenth in value* 318*000 pounds worth $33*704. Quantity taken and value have increased since 1920* but relative importance has dropped. Anderson and Power (1955) reported that the 1955 catch in Chesapeake Bay was 873*000 pounds worth $94*000* ranked sixteenth and thirteenth* respec­ tively* among migratory food fishes. In 1955 in the United States 1*386*000 pounds of eels* worth $186*000* were landed. Chesapeake Bay.landings were 63 per cent by weight, and about 50 per cent by value* of this total. If eels were in greater demand in the United States* landings undoubtedly could be increased considerably, for the resource now is underexploited. rv. The eel is considered by some to be very destructive of other fish. This belief was so strong in the latter part of the nineteenth century that a bounty was paid by the State of Maryland for their destruction. Eels probably are no more voracious than other predatory fishes* such as striped bass* but their superficial resemblance to the parasitic lamprey may have been responsible for this strong public feeling. However* they * » i • - £ ; J # 4 O * * V J ' - do cause trouble by entering crab shedding floats and by damaging shad and other fishes in gill nets. The importance of anchovies as food for other fishes is greater '' i • ft • t. ^ : . ; ; . 'u than their direct importance to man. Hildebrand and Schroeder (1927) • • t ' * ■ t - • v* - • .VO ■ • ' ‘ stated that the abundance of A. mitchilli in Chesapeake Bay and its - 2 - tributaries was second only to the silverside, Menidia roenidia. Results of trawling surveys by the Virginia Fisheries Laboratory suggest that they are one of the roost important forage fishes, rivalling even menhaden in abundance, Hildebrand (1943) suggested that the anchovy was the most important single item of food for large predatory fishes in the middle and south Atlantic and Central America regions, especially for sea trouts, bluefish, Spanish mackerel, bonito and dolphin, t^e Old World, members of the family Engraulidae are preserved ,by salting, smoking, as anchovy paste, and in other ways. The smallness of. most native anchovies prohibited their early exploitation in North America but the quantity marketed in the past twenty years has increased rapidly. Production by the United States and Alaska in 1955 (Anderson \and Power, 1955) was 44,714,000 pounds worth approximately $597,000. This catch consisted almost entirely of Engraulis mordax, the large Pacific northern anchovy, that ranges from British Columbia to Lower California. Anchovies also are used as bait in tuna fisheries along the west coast as far. south as Panama Bay and in South America, where some species reach 10 to 12 inches or more (Hildebrand, 1943). ; u .f -i n; , - * - ■ -f. ?■■*. j v'ef’chcft t * s i x History and Purpose of Meristic Studies t:- c c ■ ■ > . * '• r’ - ‘ ’■"» : / ‘ Geographical variation in fishes has interested biologists for ? ■* • op .* a ■ .. * „ . • r « i • * *1" ■' *- ' “ *• the past 60 years. David Starr Jordan, the famous American ichthyologist, in 1892 was the first, to recognize that numbers of vertebrae in fishes * r " . r * • t '***-£ iC 1 - ' r- '»Z vary from north to south, and he related this variation to the effects of temperature, proposing the general law that species from northern wafers tended to have larger numbers of vertebrae than those from the - 3 - tropics. Friedrich Heincke (1898) first demonstrated clearly that this principle could be applied to local groups within a single species by showing that mean number of vertebrae in Clupea harengus, the Atlantic herring, decreased from north to south. Johannes Schmidt (1920) showed that mean numbers of vertebrae were inherited, but that they could be altered by varying temperatures during embryonic development. .r x <H < c/ - These findings provided