Mate limitation in sea lice infesting wild salmon hosts: the influence of parasite sex ratio and aggregation

R. Cox, M. L. Groner, C. D. Todd, G. Gettinby, T. Patanasatienkul, C. W. Revie

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Mate limitation in dioecious parasite species has the potential to impact parasite population growth. Our focus of interest was the influence of parasite sex distribution among hosts on parasite reproduction and transmission dynamics for populations of ectoparasitic sea lice (Lepeophtheirus salmonis Krøyer) establishing on wild juvenile salmon hosts. The data included more than 139,000 out-migrating juvenile pink salmon (Oncorhynchus gorbuscha (Walbaum)) and chum salmon (Oncorhynchus keta (Walbaum)) in British Columbia, Canada, sampled over nine years. For almost all years, the sex ratio of the reproductive stages of the sea lice was female-biased. The probability of a female being able to mate (i.e., of being attached to a fish also carrying a male louse) increased with increasing parasite abundance and parasite aggregation. We compared, with expected modeling predictions, the observed prevalence of pairs of sea lice (i.e., one reproductive louse of each sex) on a given fish and the observed probability of a female being able to mate. These comparisons showed that male and female sea lice tend to be distributed together rather than separately on hosts. Distribution together means that sea lice are distributed randomly on hosts according to a common negative binomial distribution, whereas distribution separately means that males are distributed according to a negative binomial and females are distributed in their own negative binomial among hosts. Despite the tendency for distribution together we found that, in every year, at least 30% of reproductive female sea lice experience mate limitation. This Allee effect will result in submaximal rates of parasite reproduction at low parasite abundances and may limit parasite transmission. The work has important implications for salmon parasite management and the health both of captive farm salmon populations and migratory wild stocks. More broadly, these results demonstrate the potential impact of mate limitation as a constraint to the establishment and spread of wild ectoparasite populations.

LanguageEnglish
Article numbere02040
Number of pages19
JournalEcosphere
Volume8
Issue number12
Early online date27 Dec 2017
DOIs
Publication statusPublished - 31 Dec 2017

Fingerprint

Lepeophtheirus salmonis
sex ratio
salmon
parasite
parasites
louse
Oncorhynchus gorbuscha
Oncorhynchus keta
lice
parasite transmission
Allee effect
sea
ectoparasite
fish
gender
ectoparasites
population growth
British Columbia
distribution
farm

Keywords

  • dioecious parasite
  • host-parasite interactions
  • mate limitation
  • sea lice
  • sex ratio
  • wild salmon
  • computational modelling

Cite this

Cox, R. ; Groner, M. L. ; Todd, C. D. ; Gettinby, G. ; Patanasatienkul, T. ; Revie, C. W. / Mate limitation in sea lice infesting wild salmon hosts : the influence of parasite sex ratio and aggregation. In: Ecosphere. 2017 ; Vol. 8, No. 12.
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abstract = "Mate limitation in dioecious parasite species has the potential to impact parasite population growth. Our focus of interest was the influence of parasite sex distribution among hosts on parasite reproduction and transmission dynamics for populations of ectoparasitic sea lice (Lepeophtheirus salmonis Kr{\o}yer) establishing on wild juvenile salmon hosts. The data included more than 139,000 out-migrating juvenile pink salmon (Oncorhynchus gorbuscha (Walbaum)) and chum salmon (Oncorhynchus keta (Walbaum)) in British Columbia, Canada, sampled over nine years. For almost all years, the sex ratio of the reproductive stages of the sea lice was female-biased. The probability of a female being able to mate (i.e., of being attached to a fish also carrying a male louse) increased with increasing parasite abundance and parasite aggregation. We compared, with expected modeling predictions, the observed prevalence of pairs of sea lice (i.e., one reproductive louse of each sex) on a given fish and the observed probability of a female being able to mate. These comparisons showed that male and female sea lice tend to be distributed together rather than separately on hosts. Distribution together means that sea lice are distributed randomly on hosts according to a common negative binomial distribution, whereas distribution separately means that males are distributed according to a negative binomial and females are distributed in their own negative binomial among hosts. Despite the tendency for distribution together we found that, in every year, at least 30{\%} of reproductive female sea lice experience mate limitation. This Allee effect will result in submaximal rates of parasite reproduction at low parasite abundances and may limit parasite transmission. The work has important implications for salmon parasite management and the health both of captive farm salmon populations and migratory wild stocks. More broadly, these results demonstrate the potential impact of mate limitation as a constraint to the establishment and spread of wild ectoparasite populations.",
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Mate limitation in sea lice infesting wild salmon hosts : the influence of parasite sex ratio and aggregation. / Cox, R.; Groner, M. L.; Todd, C. D.; Gettinby, G.; Patanasatienkul, T.; Revie, C. W.

In: Ecosphere, Vol. 8, No. 12, e02040, 31.12.2017.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Mate limitation in sea lice infesting wild salmon hosts

T2 - Ecosphere

AU - Cox, R.

AU - Groner, M. L.

AU - Todd, C. D.

AU - Gettinby, G.

AU - Patanasatienkul, T.

AU - Revie, C. W.

PY - 2017/12/31

Y1 - 2017/12/31

N2 - Mate limitation in dioecious parasite species has the potential to impact parasite population growth. Our focus of interest was the influence of parasite sex distribution among hosts on parasite reproduction and transmission dynamics for populations of ectoparasitic sea lice (Lepeophtheirus salmonis Krøyer) establishing on wild juvenile salmon hosts. The data included more than 139,000 out-migrating juvenile pink salmon (Oncorhynchus gorbuscha (Walbaum)) and chum salmon (Oncorhynchus keta (Walbaum)) in British Columbia, Canada, sampled over nine years. For almost all years, the sex ratio of the reproductive stages of the sea lice was female-biased. The probability of a female being able to mate (i.e., of being attached to a fish also carrying a male louse) increased with increasing parasite abundance and parasite aggregation. We compared, with expected modeling predictions, the observed prevalence of pairs of sea lice (i.e., one reproductive louse of each sex) on a given fish and the observed probability of a female being able to mate. These comparisons showed that male and female sea lice tend to be distributed together rather than separately on hosts. Distribution together means that sea lice are distributed randomly on hosts according to a common negative binomial distribution, whereas distribution separately means that males are distributed according to a negative binomial and females are distributed in their own negative binomial among hosts. Despite the tendency for distribution together we found that, in every year, at least 30% of reproductive female sea lice experience mate limitation. This Allee effect will result in submaximal rates of parasite reproduction at low parasite abundances and may limit parasite transmission. The work has important implications for salmon parasite management and the health both of captive farm salmon populations and migratory wild stocks. More broadly, these results demonstrate the potential impact of mate limitation as a constraint to the establishment and spread of wild ectoparasite populations.

AB - Mate limitation in dioecious parasite species has the potential to impact parasite population growth. Our focus of interest was the influence of parasite sex distribution among hosts on parasite reproduction and transmission dynamics for populations of ectoparasitic sea lice (Lepeophtheirus salmonis Krøyer) establishing on wild juvenile salmon hosts. The data included more than 139,000 out-migrating juvenile pink salmon (Oncorhynchus gorbuscha (Walbaum)) and chum salmon (Oncorhynchus keta (Walbaum)) in British Columbia, Canada, sampled over nine years. For almost all years, the sex ratio of the reproductive stages of the sea lice was female-biased. The probability of a female being able to mate (i.e., of being attached to a fish also carrying a male louse) increased with increasing parasite abundance and parasite aggregation. We compared, with expected modeling predictions, the observed prevalence of pairs of sea lice (i.e., one reproductive louse of each sex) on a given fish and the observed probability of a female being able to mate. These comparisons showed that male and female sea lice tend to be distributed together rather than separately on hosts. Distribution together means that sea lice are distributed randomly on hosts according to a common negative binomial distribution, whereas distribution separately means that males are distributed according to a negative binomial and females are distributed in their own negative binomial among hosts. Despite the tendency for distribution together we found that, in every year, at least 30% of reproductive female sea lice experience mate limitation. This Allee effect will result in submaximal rates of parasite reproduction at low parasite abundances and may limit parasite transmission. The work has important implications for salmon parasite management and the health both of captive farm salmon populations and migratory wild stocks. More broadly, these results demonstrate the potential impact of mate limitation as a constraint to the establishment and spread of wild ectoparasite populations.

KW - dioecious parasite

KW - host-parasite interactions

KW - mate limitation

KW - sea lice

KW - sex ratio

KW - wild salmon

KW - computational modelling

U2 - 10.1002/ecs2.2040

DO - 10.1002/ecs2.2040

M3 - Article

VL - 8

JO - Ecosphere

JF - Ecosphere

SN - 2150-8925

IS - 12

M1 - e02040

ER -