UAc - Okeanos R&D Centre - University of the Azores

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Predictive model of sperm whale prey capture attempts from time-depth data

Publication . Pérez-Jorge, Sergi; Oliveira, Cláudia; Iglesias Rivas, Esteban; Prieto, Rui; Cascão, Irma; Wensveen, Paul J.; Miller, Patrick J. O.; Silva, Mónica A.

BackgroundHigh-resolution sound and movement recording tags offer unprecedented insights into the fine-scale foraging behaviour of cetaceans, especially echolocating odontocetes, enabling the estimation of a series of foraging metrics. However, these tags are expensive, making them inaccessible to most researchers. Time-Depth Recorders (TDRs), which have been widely used to study diving and foraging behaviour of marine mammals, offer a more affordable alternative. Unfortunately, data collected by TDRs are bi-dimensional (time and depth only), so quantifying foraging effort from those data is challenging.MethodsA predictive model of the foraging effort of sperm whales (Physeter macrocephalus) was developed to identify prey capture attempts (PCAs) from time-depth data. Data from high-resolution acoustic and movement recording tags deployed on 12 sperm whales were downsampled to 1 Hz to match the typical TDR sampling resolution and used to predict the number of buzzes (i.e., rapid series of echolocation clicks indicative of PCAs). Generalized linear mixed models were built for dive segments of different durations (30, 60, 180 and 300 s) using multiple dive metrics as potential predictors of PCAs.ResultsAverage depth, variance of depth and variance of vertical velocity were the best predictors of the number of buzzes. Sensitivity analysis showed that models with segments of 180 s had the best overall predictive performance, with a good area under the curve value (0.78 +/- 0.05), high sensitivity (0.93 +/- 0.06) and high specificity (0.64 +/- 0.14). Models using 180 s segments had a small difference between observed and predicted number of buzzes per dive, with a median of 4 buzzes, representing a difference in predicted buzzes of 30%.ConclusionsThese results demonstrate that it is possible to obtain a fine-scale, accurate index of sperm whale PCAs from time-depth data alone. This work helps leveraging the potential of time-depth data for studying the foraging ecology of sperm whales and the possibility of applying this approach to a wide range of echolocating cetaceans. The development of accurate foraging indices from low-cost, easily accessible TDR data would contribute to democratize this type of research, promote long-term studies of various species in several locations, and enable analyses of historical datasets to investigate changes in cetacean foraging activity.

2023Journal article

Open access

A methodology for shipping noise field calibration and excess noise estimation: the Azores case study

Publication . Jesus, Sergio; Soares, Cristiano; Romagosa, Miriam; Cascão, Irma; Duarte, Ricardo; Zabel, Friedrich; Silva, Mónica A.

Economic globalization and the continuous search for food, energy and raw materials led to an estimated 3 dB/decade increase of ocean noise intensity. Determining the level of anthropogenic noise, the so-called excess noise, and building identifiable meaningful indicators for supporting marine management policies currently requires extensive observation data and computer modeling. For modeling purposes, in this study, anthropogenic noise was reduced to shipping traffic drawn from Automatic Identification System data, and environmental sound was attributed to surface wind only. Data-model comparison allowed introducing a methodology for simple model calibration and estimate excess noise. This methodology was tested on acoustic recordings performed in June 2018 at three locations to the southwest of Faial-Pico Islands in the Azores archipelago. The results show that field-calibrated excess noise sound maps are in line with the shipping distribution in the area, revealing a number of potentially marine life-threatening hotspots. Excess noise addresses the need for a quantifiable measure of ocean noise only and therefore offers a basis for building suitable continuous anthropogenic noise pollution indicators.

2022-11-16Journal article

Open access

Application of scientific criteria for identifying hydrothermal ecosystems in need of protection

Publication . Gollner, S.; Colaço, A.; Gebruk, A.; Halpin, P. N.; Higgs, N.; Menini, E.; Mestre, Nélia; Qian, P. Y.; Sarrazin, J.; Szafranski, K.; Van Dover, C. L.

Deep-sea hydrothermal vent fields are globally rare (abundant in numbers, but extremely small in area) and are rich in extraordinary life based on chemosynthesis rather than photosynthesis. Vent fields are also sources of polymetallic sulfides rich in copper and other metals. Mineral resources of the international seabed beyond national jurisdictions (referred to as the “Area”) are administered by the International Seabed Authority (ISA), which has the mandate to organize and control mineral resource-related activities and to ensure effective protection of the marine environment from harmful effects which may arise from such activities. To date, the ISA has approved 3 contracts for mineral exploration on the northern Mid-Atlantic Ridge (nMAR) and is developing a Regional Environmental Management Plan (REMPs) for polymetallic sulfide resources in the Area of northern MAR, including the application of area-based management tools to address the potential impacts of mining activities. Several intergovernmental organizations have developed suites of criteria to identify vulnerable, sensitive, and ecologically or biologically significant ecosystems in need of protection. In this case study, we combine criteria developed by FAO for VMEs (Vulnerable Marine Ecosystems), by CBD for EBSAs (Ecologically or Biologically Significant Areas), and by IMO for PSSAs (Particularly Sensitive Sea Areas) to assess whether the 11 confirmed vent fields on the nMAR may meet these criteria. Our assessment indicates that all vent fields meet multiple criteria for vulnerability, sensitivity, and ecological or biological significance, and 10 of 11 vent fields meet all criteria for ecosystems in need of protection.

2021-10Journal article

Open access

Global habitat predictions to inform spatiotemporal fisheries management: initial steps within the framework

Publication . Bowlby, Heather D.; Druon, Jean-Noël; Lopez, Jon; Juan-Jordá, Maria José; Carreón-Zapiain, María Teresa; Vandeperre, Frederic; Leone, Agostino; Finucci, Brittany; Sabarros, Philippe S.; Block, Barbara A.; Arrizabalaga, Haritz; Afonso, Pedro; Musyl, Michael K.; Cortés, Enric; Cardoso, Luis Gustavo; Mourato, Bruno; Queiroz, Nuno; Fontes, Jorge; Abascal, Francisco J.; Zanzi, Antonella; Hazin, Humberto Gomes; Bach, Pascal; Sims, David W.; Travassos, Paulo; Coelho, Rui

Tuna Regional Fishery Management Organizations (tRFMOs) are increasingly interested in spatiotemporal management as a tool to reduce interaction rates with vulnerable species. We use blue shark ( Prionace glauca ) as a case study to demonstrate the critical first steps in the implementation process, highlighting how predictions of global habitat for vulnerable life stages can be transformed into a publicly -accessible spatial bycatch mitigation tool. By providing examples of possible management goals and an associated threshold to identify essential habitats, we show how these key areas can represent a relatively low percentage of oceanic area on a monthly basis (16-24% between 50 degrees S and 60 degrees N), yet can have relatively high potential protection efficiency (similar to 42%) for vulnerable stages if fishing effort is redistributed elsewhere. While spatiotemporal management has demonstrable potential for blue sharks to effectively mitigate fishing mortality on sensitive life stages, we identify inherent challenges and sequential steps that require careful consideration by tRFMOs as work proceeds. We also discuss how our single-species framework could be easily extended to a multispecies approach by assigning relative conservation risk before layering habitat model predictions in an integrated analysis. Such broader application of our approach could address the goals of tRFMOs related to reducing the ecosystem effects of fishing and pave the way for efficient fisheries co-management using an ecosystem-based approach.

2024-06Journal article

Open access