MARE - Marine and Environmental Sciences Centre

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Publications

Assessment of catches, landings and fishing effort as useful tools for MPA management

Publication . Batista, Marisa I.; Costa, Bárbara Horta e; Gonçalves, Leonel; Henriques, Miguel; Erzini, Karim; Caselle, Jennifer E.; Gonçalves, Emanuel João; Cabral, Henrique

Marine protected areas (MPAs) have been widely recognized as a tool to achieve both fisheries management and conservation goals. Simultaneously achieving these multiple goals is difficult due to conflicts between conservation (often long-term) and economic (often short-term) objectives. MPA implementation often includes additional control measures on fisheries (e.g. vessel size restrictions, gear exclusion, catch controls) that in the short-term may have impacts on local fishers’ communities. Thus, monitoring fisheries catches before, during and after MPA implementation is essential to document changes in fisheries activities and to evaluate the impact of MPAs in fishers’ communities. Remarkably, in contrast with standard fisheries-independent biological surveys, these data are rarely measured at appropriate spatial scales following MPA implementation. Here, the effects of MPA implementation on local fisheries are assessed in a temperate MPA (Arrábida Marine Park, Portugal), using fisheries monitoring methods combining spatial distribution of fishing effort, on-board observations and official landings statistics at scales appropriate to the Marine Park. Fisheries spatial distribution, fishing effort, on-board data collection and official landings registered for the same vessels over time were analysed between 2004 and 2010. The applicability and reliability of using landings statistics alone was tested (i.e. when no sampling data are available) and we conclude that landings data alone only allow the identification of general patterns. The combination of landings information (which is known to be unreliable in many coastal communities) with other methods, provides an effective tool to evaluate fisheries dynamics in response to MPA implementation. As resources for monitoring socio-ecological responses to MPAs are frequently scarce, the use of landings data calibrated with fisheries information (from vessels, gear distribution and on-board data) is a valuable tool applicable to many worldwide coastal small-scale fisheries.

2015Journal article

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A quantitative analysis of pulsed signals emitted by wild bottlenose dolphinsof Pulsed Signals Emitted by Wild Bottlenose Dolphins

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Growth and age structure in captive and wild stocks of the endangered western ruivaco Achondrostoma occidentale (Cyprinidae)

Publication . Mameri, D.; Santos, Carla Sousa; Robalo, Joana Isabel

Declines in freshwater fish populations are occurring at a fast rate, increasing the importance of ex-situ conservation programs supported by sound knowledge of population dynamics and life-history traits of the target species. We analysed the growth and age structure of wild and captive stocks of the western ruivaco Achondrostoma occidentale, a Portuguese endangered cyprinid, targeted for captive breeding and restocking since 2007. Specifically, we compared maximum size, longevity, and length-at-age among captive and wild populations, restocked and non-restocked. We found considerable variation in length-at-age and longevity between captive-bred and wild fish, with the former generally growing faster and living longer. Analysis of length-age distributions among wild populations suggested a positive effect of restocking actions in fish abundance. Results highlight the value of captive breeding for the conservation of endangered cyprinids, and reinforce the need for detailed data on life-history trait variation between captive and wild stocks to assess the efficiency of ex-situ conservation programs.

2018Journal article

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A Quantitative analysis of pulsed signals emitted by Wild Bottlenose Dolphins

Publication . Luís, Ana Rita; Couchinho, Miguel N.; dos Santos, Manuel E.

Common bottlenose dolphins (Tursiops truncatus), produce a wide variety of vocal emissions for communication and echolocation, of which the pulsed repertoire has been the most difficult to categorize. Packets of high repetition, broadband pulses are still largely reported under a general designation of burst-pulses, and traditional attempts to classify these emissions rely mainly in their aural characteristics and in graphical aspects of spectrograms. Here, we present a quantitative analysis of pulsed signals emitted by wild bottlenose dolphins, in the Sado estuary, Portugal (2011-2014), and test the reliability of a traditional classification approach. Acoustic parameters (minimum frequency, maximum frequency, peak frequency, duration, repetition rate and inter-click-interval) were extracted from 930 pulsed signals, previously categorized using a traditional approach. Discriminant function analysis revealed a high reliability of the traditional classification approach (93.5% of pulsed signals were consistently assigned to their aurally based categories). According to the discriminant function analysis (Wilk's Λ = 0.11, F3, 2.41 = 282.75, P < 0.001), repetition rate is the feature that best enables the discrimination of different pulsed signals (structure coefficient = 0.98). Classification using hierarchical cluster analysis led to a similar categorization pattern: two main signal types with distinct magnitudes of repetition rate were clustered into five groups. The pulsed signals, here described, present significant differences in their time-frequency features, especially repetition rate (P < 0.001), inter-click-interval (P < 0.001) and duration (P < 0.001). We document the occurrence of a distinct signal type-short burst-pulses, and highlight the existence of a diverse repertoire of pulsed vocalizations emitted in graded sequences. The use of quantitative analysis of pulsed signals is essential to improve classifications and to better assess the contexts of emission, geographic variation and the functional significance of pulsed signals.

2016Journal article

Open access

Predicting the effects of anthropogenic noise on fish reproduction

Publication . Jong, Karen De; Forland, Tonje Nesse; Amorim, Maria Clara Pessoa; Rieucau, Guillaume; Slabbekoorn, Hans; Sivle, Lise Doksæter

Aquatic animals use and produce sound for critical life functions, including reproduction. Anthropogenic noise is recognized as a global source of environmental pollution and adequate conservation and management strategies are urgently needed. It becomes therefore critical to identify the reproductive traits that render a species vulnerable to acoustic disturbances, and the types of anthropogenic noise that are most likely to impact reproduction. Here, we provide predictions about noise impact on fish reproduction following a two-step approach: first, we grouped documented effects of noise into three mechanistic categories: stress, masking and hearing-loss, and test which type of noise (continuous vs intermittent and regular vs irregular) was most likely to produce a significant response in each category with either ametaanalysis or a quantitative review, depending on data availability. Second, we reviewed existing literature to predictwhich reproductive traits would render fish most sensitive to stress, masking and hearing-loss. In step one, we concluded that continuous sounds with irregular amplitude and/or frequency-content (e.g. heavy ship traffic) were most likely to cause stress, and continuous sounds were also most likely to induce masking and hearing-loss. From step two we concluded that the vulnerability of a species to noise-induced stress will mainly depend on: (1) its potential to reallocate reproduction to more quiet times or locations, and (2) its vulnerability to masking and hearing-loss mainly on the function of sound communication in its reproductive behaviour. We discuss in which stages of reproduction fish are most likely to be vulnerable to anthropogenic noise based on these findings.

2020Journal article

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