DOI: 10.5061/dryad.p2ngf1vp3
title: Life history shifts in an exploited African fish following invasion by a castrating parasite

description: Evolutionary theory predicts that infection by a parasite that reduces
 future host survival or fecundity should select for increased investment
 in current reproduction. In this study we use the
 cestode Ligula intestinalis and its intermediate fish
 host Engraulicypris sardella in Wissman Bay,
 Lake Nyasa (Tanzania) as a model system. Using
 data about infection of E. sardella fish hosts
 by L. intestinalis collected for a period of 10 years,
 we explored whether parasite infection affects the fecundity of the fish
 host E. sardella, and whether host reproductive investment has
 increased at the expense of somatic growth. We found that L.
 intestinalis had a strong negative effect on the fecundity of its
 intermediate fish host. For the non-infected fish we observed an increase
 in relative gonadal weight at maturity over the study period, while size
 at maturity decreased. These findings suggest that the life history
 of E. sardella has been shifting towards earlier
 reproduction. Further studies are warranted to assess whether these
 changes reflect plastic or evolutionary responses. We also discuss the
 interaction between parasite and fishery-mediated selection as a possible
 explanation for the decline of E. sardella stock in the
 lake.
description: Data_usipa_all_wissman.txt (used for analyses and figures 2-3
 & A2) Month2 – continuous month count
 (1=January 2005)<br> Day – calendar day<br> Month – calendar
 month<br> Year – calendar year<br> Season – dry/wet
 season<br> Length_usipa – body length in mm<br> Weight_usipa –
 body weight in g<br> Sex_usipa - sex<br> Maturity_stage –
 maturity stage<br> Maturity_status – 0: stages I-III, 1: stages
 IV-VII<br> Postmaturity_status – 0: stages I-IV, 1: stages
 V-VII<br> Ligula_count – number of individual parasites
 found<br> Infection – 0: non-infected, 1: infected<br>
 Weight_gonad – wet weight of gonads<br> Number_eggs – number of eggs
 counted in gonads<br> Somatic_weight – calculated as (total weight –
 weight of gonads)<br> GSI – gonadosomatic index in %<br>
 Condition_factor – Fulton index<br> Repro_status – 0: pre-spawn, 1:
 ready to spawn or post-spawn Yearlydata.txt (used for
 analysis and figures 3 & A3) Year – calendar
 year<br> Inf_peakfec – number of infected fish at stages
 IV-V<br> Total_peakfec – total number of fish at stages
 IV-V<br> Prev_peakfec – prevalence at stages IV-V<br>
 Inf_mature- number of infected fish at stages IV-VII<br>
 Total_mature – total number of fish at stages IV-VII<br> Prev_mature
 – prevalence at stages IV-VII<br> Inf_immat - number of infected
 fish at stages I-III<br> Total_immat - total number of fish at
 stages I-III<br> Prev_immat – prevalence at stages I-III<br>
 Inf_all – number of infected fish, all stages<br> Total – total
 number of fish<br> Prev_all – prevalence, all stages<br>
 Rel-abund_immat – relative abundance of stages I-III<br>
 Rel-abund_peakfec – relative abundance of stages IV-V<br>
 Rel-abund_mat – relative abundance of stages IV-VII<br> LM50_all –
 LM50 for all fish<br> LM50_inf – LM50 for infected fish
 only<br> LM50_uninf – LM50 for uninfected fish only<br>
 Number_of_fishermen – number of fishermen registered<br>
 Fishing_pressure – number of fishermen per tonne landed<br>
 Landed_per_fisherman –number of tonnes landed per fisherman