Spatial and ontogenetic variation in growth of nursery-bound juvenile lemon sharks, Negaprion brevirostris

A comparison of two age-assigning techniques

Michael James Barker, Samuel H. Gruber, Steven P. Newman, Vera Schluessel

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

We compared growth rates of the lemon shark, Negaprion brevirostris, from Bimini, Bahamas and the Marquesas Keys (MK), Florida using data obtained in a multi-year annual census. We marked new neonate and juvenile sharks with unique electronic identity tags in Bimini and in the MK we tagged neonate and juvenile sharks. Sharks were tagged with tiny, subcutaneous transponders, a type of tagging thought to cause little, if any disruption to normal growth patterns when compared to conventional external tagging. Within the first 2 years of this project, no age data were recorded for sharks caught for the first time in Bimini. Therefore, we applied and tested two methods of age analysis: (1) a modified 'minimum convex polygon' method and (2) a new age-assigning method, the 'cut-off technique'. The cut-off technique proved to be the more suitable one, enabling us to identify the age of 134 of the 642 previously unknown aged sharks. This maximised the usable growth data included in our analysis. Annual absolute growth rates of juvenile, nursery-bound lemon sharks were almost constant for the two Bimini nurseries and can be best described by a simple linear model (growth data was only available for age-0 sharks in the MK). Annual absolute growth for age-0 sharks was much greater in the MK than in either the North Sound (NS) and Shark Land (SL) at Bimini. Growth of SL sharks was significantly faster during the first 2 years of life than of the sharks in the NS population. However, in MK, only growth in the first year was considered to be reliably estimated due to low recapture rates. Analyses indicated no significant differences in growth rates between males and females for any area.

Original languageEnglish
Pages (from-to)343-355
Number of pages13
JournalEnvironmental Biology of Fishes
Volume72
Issue number3
DOIs
StatePublished - Mar 1 2005

Fingerprint

Negaprion brevirostris
shark
sharks
methodology
neonate
tagging
neonates
comparison
transponders
Bahamas
electronics
polygon

Keywords

  • Carcharhinidae
  • Elasmobranchs
  • Florida Keys
  • Passive Integrated Transponder
  • Tag-recapture

ASJC Scopus subject areas

  • Aquatic Science
  • Ecology

Cite this

Spatial and ontogenetic variation in growth of nursery-bound juvenile lemon sharks, Negaprion brevirostris : A comparison of two age-assigning techniques. / Barker, Michael James; Gruber, Samuel H.; Newman, Steven P.; Schluessel, Vera.

In: Environmental Biology of Fishes, Vol. 72, No. 3, 01.03.2005, p. 343-355.

Research output: Contribution to journalArticle

Barker, Michael James ; Gruber, Samuel H. ; Newman, Steven P. ; Schluessel, Vera. / Spatial and ontogenetic variation in growth of nursery-bound juvenile lemon sharks, Negaprion brevirostris : A comparison of two age-assigning techniques. In: Environmental Biology of Fishes. 2005 ; Vol. 72, No. 3. pp. 343-355.
@article{8f2a29c06d2e400eb4817ac17c1543cf,
title = "Spatial and ontogenetic variation in growth of nursery-bound juvenile lemon sharks, Negaprion brevirostris: A comparison of two age-assigning techniques",
abstract = "We compared growth rates of the lemon shark, Negaprion brevirostris, from Bimini, Bahamas and the Marquesas Keys (MK), Florida using data obtained in a multi-year annual census. We marked new neonate and juvenile sharks with unique electronic identity tags in Bimini and in the MK we tagged neonate and juvenile sharks. Sharks were tagged with tiny, subcutaneous transponders, a type of tagging thought to cause little, if any disruption to normal growth patterns when compared to conventional external tagging. Within the first 2 years of this project, no age data were recorded for sharks caught for the first time in Bimini. Therefore, we applied and tested two methods of age analysis: (1) a modified 'minimum convex polygon' method and (2) a new age-assigning method, the 'cut-off technique'. The cut-off technique proved to be the more suitable one, enabling us to identify the age of 134 of the 642 previously unknown aged sharks. This maximised the usable growth data included in our analysis. Annual absolute growth rates of juvenile, nursery-bound lemon sharks were almost constant for the two Bimini nurseries and can be best described by a simple linear model (growth data was only available for age-0 sharks in the MK). Annual absolute growth for age-0 sharks was much greater in the MK than in either the North Sound (NS) and Shark Land (SL) at Bimini. Growth of SL sharks was significantly faster during the first 2 years of life than of the sharks in the NS population. However, in MK, only growth in the first year was considered to be reliably estimated due to low recapture rates. Analyses indicated no significant differences in growth rates between males and females for any area.",
keywords = "Carcharhinidae, Elasmobranchs, Florida Keys, Passive Integrated Transponder, Tag-recapture",
author = "Barker, {Michael James} and Gruber, {Samuel H.} and Newman, {Steven P.} and Vera Schluessel",
year = "2005",
month = "3",
day = "1",
doi = "10.1007/s10641-004-2584-3",
language = "English",
volume = "72",
pages = "343--355",
journal = "Environmental Biology of Fishes",
issn = "0378-1909",
publisher = "Springer Netherlands",
number = "3",

}

TY - JOUR

T1 - Spatial and ontogenetic variation in growth of nursery-bound juvenile lemon sharks, Negaprion brevirostris

T2 - A comparison of two age-assigning techniques

AU - Barker, Michael James

AU - Gruber, Samuel H.

AU - Newman, Steven P.

AU - Schluessel, Vera

PY - 2005/3/1

Y1 - 2005/3/1

N2 - We compared growth rates of the lemon shark, Negaprion brevirostris, from Bimini, Bahamas and the Marquesas Keys (MK), Florida using data obtained in a multi-year annual census. We marked new neonate and juvenile sharks with unique electronic identity tags in Bimini and in the MK we tagged neonate and juvenile sharks. Sharks were tagged with tiny, subcutaneous transponders, a type of tagging thought to cause little, if any disruption to normal growth patterns when compared to conventional external tagging. Within the first 2 years of this project, no age data were recorded for sharks caught for the first time in Bimini. Therefore, we applied and tested two methods of age analysis: (1) a modified 'minimum convex polygon' method and (2) a new age-assigning method, the 'cut-off technique'. The cut-off technique proved to be the more suitable one, enabling us to identify the age of 134 of the 642 previously unknown aged sharks. This maximised the usable growth data included in our analysis. Annual absolute growth rates of juvenile, nursery-bound lemon sharks were almost constant for the two Bimini nurseries and can be best described by a simple linear model (growth data was only available for age-0 sharks in the MK). Annual absolute growth for age-0 sharks was much greater in the MK than in either the North Sound (NS) and Shark Land (SL) at Bimini. Growth of SL sharks was significantly faster during the first 2 years of life than of the sharks in the NS population. However, in MK, only growth in the first year was considered to be reliably estimated due to low recapture rates. Analyses indicated no significant differences in growth rates between males and females for any area.

AB - We compared growth rates of the lemon shark, Negaprion brevirostris, from Bimini, Bahamas and the Marquesas Keys (MK), Florida using data obtained in a multi-year annual census. We marked new neonate and juvenile sharks with unique electronic identity tags in Bimini and in the MK we tagged neonate and juvenile sharks. Sharks were tagged with tiny, subcutaneous transponders, a type of tagging thought to cause little, if any disruption to normal growth patterns when compared to conventional external tagging. Within the first 2 years of this project, no age data were recorded for sharks caught for the first time in Bimini. Therefore, we applied and tested two methods of age analysis: (1) a modified 'minimum convex polygon' method and (2) a new age-assigning method, the 'cut-off technique'. The cut-off technique proved to be the more suitable one, enabling us to identify the age of 134 of the 642 previously unknown aged sharks. This maximised the usable growth data included in our analysis. Annual absolute growth rates of juvenile, nursery-bound lemon sharks were almost constant for the two Bimini nurseries and can be best described by a simple linear model (growth data was only available for age-0 sharks in the MK). Annual absolute growth for age-0 sharks was much greater in the MK than in either the North Sound (NS) and Shark Land (SL) at Bimini. Growth of SL sharks was significantly faster during the first 2 years of life than of the sharks in the NS population. However, in MK, only growth in the first year was considered to be reliably estimated due to low recapture rates. Analyses indicated no significant differences in growth rates between males and females for any area.

KW - Carcharhinidae

KW - Elasmobranchs

KW - Florida Keys

KW - Passive Integrated Transponder

KW - Tag-recapture

UR - http://www.scopus.com/inward/record.url?scp=17744372334&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=17744372334&partnerID=8YFLogxK

U2 - 10.1007/s10641-004-2584-3

DO - 10.1007/s10641-004-2584-3

M3 - Article

VL - 72

SP - 343

EP - 355

JO - Environmental Biology of Fishes

JF - Environmental Biology of Fishes

SN - 0378-1909

IS - 3

ER -