Towards sustainable commercial vendace fisheries in                     Finland: lessons learned from educating stakeholders for management decision                     making based on imprecise stock monitoring data

Marjomäki, Timo J.; Valkeajärvi, Pentti; Keskinen, Tapio; Muje, Kari; Urpanen, Olli

doi:10.1127/adv_limnol/2021/0068

Cited by 6 publications

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“…Graphs of (A) the proportional index of the spawning stock of Vendace in autumn and the index of recruitment (age 0) from that spawning 1 year later in Lake Etelä‐Konnevesi for 1980–2010 (data from Valkeajärvi and Marjomäki 2013; Marjomäki et al 2021c) and (B) the average age of the spawning stock given in full years (1 = two growing seasons in autumn) of mature (age ≥1) Vendace in Lake Etelä‐Konnevesi and the hypothetical sex ratio (estimated number of female spawners per one male based on the 50%:50% adjusted predicted sex ratio in Table 1). …”

Section: Resultsmentioning

confidence: 99%

Males die young, which may cause an Allee effect during a population collapse of the Vendace Coregonus albula

Marjomäki,

Valkeajärvi,

Karjalainen

2023

Trans Am Fish Soc

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ObjectiveWe estimated the difference in mortality between mature male and female Vendace Coregonus albula based on a large data set of catch samples from 25 locations in Finland. We then used this estimate and age distribution data from Lake Etelä‐Konnevesi to illustrate how the sex ratio (females per one male) might decrease as the average age of spawners increases during a several‐year‐long period of recruitment failure.MethodsWe estimated mortalities first from sex‐specific age–ln(catch) curves and second from the average age‐specific proportions of different sexes.ResultThe estimate of the additional mortality of males was around 0.2–0.4, depending on the method of estimation, and assumed true proportions in the population at age 1 (two growing seasons), when Vendace reaches sexual maturity. When using the additional mortality estimate and age distribution data from Lake Etelä‐Konnevesi, the hypothetical sex ratio in the most extreme year was even as skewed as four females per one male.ConclusionIf the lack of males per female spawner during a population decline reduces the per capita recruitment success of females, this is a depensatory density‐dependent effect, the Allee effect. This phenomenon may partly explain the rapid population collapses and contribute to 2‐year cyclicity typical of the dynamics of Vendace populations.

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Section: Resultsmentioning

confidence: 99%

Males die young, which may cause an Allee effect during a population collapse of the Vendace Coregonus albula

Marjomäki,

Valkeajärvi,

Karjalainen

2023

Trans Am Fish Soc

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Genetic-based evaluation of management units for sustainable vendace (Coregonus albula) fisheries in a large lake system

et al. 2022

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Vendace populations on the life table: between-lake variation and the association between early life and mature survival and growth

Marjomäki,

Auvinen,

Helminen

et al. 2024

Int. J. Lim.

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The vital rates related to reproduction and survival dictate the resistance and persistence of a population under perturbations. Freshwater fishes perform high levels of phenotypic plasticity thus these rates may differ widely between populations and temporally within a population. Knowledge of their ranges enables understanding the scope of population persistence and predicting the effects of environmental stressors. Time series of vendace (Coregonus albula) catch samples from 22 lakes were applied to estimate the lake-specific average length-at-age and survival in mature age groups (mS). Assuming an age-at-maturity of 2 yr and a constant length–fecundity relationship, survival from spawning to age 1 (firstS) and 2 (premS, prematurity survival) were estimated using a life table assuming a stable state. The average length at age 2 yr (L2) varied two-fold between populations, <100 – > 200 mm, and the estimated fecundity approximately eight-fold. Also, mS varied considerably, <10–70%a−1. L2 and mS were positively associated. The premS estimate varied ∼30-fold among lakes, <0.01 – > 0.2% per 2 yr, being highest in populations with low L2 and fecundity combined with low mS. The range of firstS estimate was even higher, 0.01–2%. This high between-lake variability seems to occur especially after hatching during the first summer. Its level is set by the factors external to the population, e.g., the abundance of key predators. Persistence with low early life survival is possible because of the wide scope of compensation in the size- and fecundity-at-age and mS. Early life survival is expected to decrease due to climate change while the compensation has its limits, increasing the risk of local extinctions.

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Towards sustainable commercial vendace fisheries in Finland: lessons learned from educating stakeholders for management decision making based on imprecise stock monitoring data

Cited by 6 publications

References 0 publications

Males die young, which may cause an Allee effect during a population collapse of the Vendace Coregonus albula

Males die young, which may cause an Allee effect during a population collapse of the Vendace Coregonus albula

Genetic-based evaluation of management units for sustainable vendace (Coregonus albula) fisheries in a large lake system

Vendace populations on the life table: between-lake variation and the association between early life and mature survival and growth

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