Demography of sea lamprey (<i>Petromyzon marinus</i>) ammocoete populations in relation to potential spawning‐migration obstructions

1. Migratory species depend on connected habitats and appropriate migratory cues to complete their life cycles. Diadromous fish exemplify species with migratory life cycles by moving between connected freshwater and saltwater habitats to reproduce. However, migration increases the exposure of fish to multiple threats and it is critical that managers integrate habitat connectivity into resource management and conservation.2. The benefit of alternative management actions was assessed for a diadromous fish, the Australian bass Percalates novemaculeata, using a spatio-temporal population model informed by individual-based movement data. The management actions comprise seasonal closures during the spawning season, and controlling fishing pressure by limiting catch or effort.3. The benefits of implementing seasonal closures depend upon interactions among how fishing pressure is controlled, the response of anglers to fishery regulations and river flow regimes.The results indicated that seasonal closures are ineffective if fishing pressure is merely displaced to another location or time of year. In addition, shifting seasonal closures from spawning grounds to feeding grounds increased population abundances under low flow events when fishing effort was also controlled. However, when total annual catch is limited by a fishery closure, changing the location of seasonal closure schemes had little effect.4. The findings in this study highlight the need for flexible management strategies that account for migratory movements and respond both to variations in connectivity (e.g. river flow regime) and direct pressures on survivorship (e.g. exploitation). As the implementation of one management action (e.g. fishing or water regulation) could affect the influence of another management action, this study emphasizes the importance of cooperation between resource managers in conserving migratory species.

Section: Connectivity Change and Consequences For Managementmentioning

confidence: 99%

Impacts of fishing, river flow and connectivity loss on the conservation of a migratory fish population

Lin

Brown

Dwyer

et al. 2017

“…Most studies investigating the impact of low‐head obstacles on anadromous lamprey migration (Andrade et al, ; Castro‐Santos, Shi, & Haro, ; Jackson & Moser, ; Lucas et al, ; Moser, Almeida, Kemp, & Sorensen, ; Nunn et al, ) have focused on the telemetry tracking of small numbers of individuals, and studies at a population level are much more scarce. As an exception, the work of Lucas et al () complemented telemetry tracking with counts of adult European river lamprey Lampetra fluviatilis (Linnaeus, 1758) at spawning grounds to evaluate the effect of weirs on these counts.…”

Section: Introductionmentioning

confidence: 99%

Upstream migration of the anadromous sea lamprey (Petromyzon marinusLinnaeus, 1758) in a highly impounded river: Impact of low‐head obstacles and fisheries

Silva

Barca

Vieira‐Lanero

et al. 2019

“…Accurate methods of assessing the state of lamprey are needed to manage commercial fisheries (Abersons & Birzaks, ; Araújo et al, ), to conserve threatened stocks in the context of habitat loss (King, Wightman, Hanna, & Gilligan, ) and river fragmentation (Nunn et al, ; Pereira et al, ), and to assess the efficacy of control measures (Maitland, Renaud, Quintella, Close, & Docker, ; Moser, Butzerin, & Dey, ). Species with prolonged juvenile stages, such as lamprey (Moser et al, ) and salmonids (Egglishaw & Shackley, ), can be sampled relatively easily by targeting appropriate habitat for this life stage (Bagenal & Nellen, ).…”

Section: Introductionmentioning

confidence: 99%

“…There is a marked contrast between the management of lamprey in the North American Great Lakes, where they are considered an invasive species with significant adverse impacts on native fish, and the conservation management perspective in the US Pacific Northwest and in Europe (Hansen et al, 2016). The European Union (EU) Habitats Directive (HD) on the conservation of natural habitats and of wild fauna and flora aims to promote the maintenance of biodiversity, taking account of economic, social, cultural, and regional requirements (Council of the European Communities, 1992 Accurate methods of assessing the state of lamprey are needed to manage commercial fisheries (Abersons & Birzaks, 2014;Araújo et al, 2016), to conserve threatened stocks in the context of habitat loss (King, Wightman, Hanna, & Gilligan, 2015) and river fragmentation (Nunn et al, 2017;Pereira et al, 2017), and to assess the efficacy of control measures (Maitland, Renaud, Quintella, Close, & Docker, 2015;Moser, Butzerin, & Dey, 2007). Species with prolonged juvenile stages, such as lamprey (Moser et al, 2007) and salmonids (Egglishaw & Shackley, 1977), can be sampled relatively easily by targeting appropriate habitat for this life stage (Bagenal & Nellen, 1980).…”

mentioning

confidence: 99%

“…In many cases (especially for smaller samples), a more qualitative approach has been applied, with the range of size/age cohorts present in a sample estimated by visual evaluation of the length-frequency distribution (Nunn et al, 2008). Favourable conservation status for lamprey ammocoetes has been defined as two or more apparent length (age) modes for abundant populations (Cowx, Harvey, Noble, & Nunn, 2010;Harvey & Cowx, 2003;Nunn et al, 2017). This approach can be time consuming and somewhat subjective.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Length‐based assessment of larval lamprey population structure at differing spatial scales

Shephard

Gallagher

Rooney

et al. 2019

Perspectives on lamprey management contrast between pest control in the US Great Lakes and species conservation in the Pacific Northwest, New Zealand, and Europe. Five lamprey species are listed in the European Union (EU) Habitats Directive (HD) as requiring conservation measures. Assessments of HD ‘conservation status’ for these lampreys mainly target the larval (ammocoete) stage. Larval lamprey populations can be assessed by evaluating presence or absence, density and demographic structure in riverine samples. Demographic structure has typically been described from length–frequency data using qualitative approaches and the statistical assignment of age classes. Length‐based indicators (LBIs) may provide a more rapid and flexible framework. The demographic structure of a fish population can be described by univariate length metrics: length range (LRANGE) and 90th percentile of length (L90). This study used a pooled data set from seven Irish catchments to estimate a reference point (RP) value for each metric corresponding to a healthy larval lamprey population. Two LBIs were then derived that can be estimated for an observed (OBS) population as LBIRANGE = LRANGE_OBS/LRANGE_RP and LBI90 = L90_OBS/L90_RP. Simulated lamprey population length structures, representing a range of status values, were used to develop a reference gradient (RG) to support population assessment using LBIs. The assessment framework was applied to each of the seven Irish catchments, and also to subcatchment and sampling‐site scales within the Barrow system. The LBIs and RG suggested that most catchments had favourable conservation status overall, whereas smaller assessment scales revealed a spread of status values. The proposed framework allows the rapid assessment of demographic structure and comparison across systems. There is potential to track states across sampling sites, events, and legislative reporting cycles, and to interpret change in relation to the local environment. The general approach may be adaptable for other fish species monitored during juvenile stages.