RESUMO
Understanding the migratory patterns of large whales is of conservation importance, especially in identifying threats to specific populations. Migration ecology, including migratory destinations, movements and site fidelity for humpback whales (Megaptera novaeangliae) remain poorly studied in parts of the range of the Central America population, considered endangered under the United States Endangered Species Act. This study aimed to investigate the migratory destinations of humpback whales sighted at two study sites in Nicaragua, which are part of the Central America population. A ten-year photographic database of humpback whales observed off Nicaragua was combined with citizen science contributions and sightings from dedicated research programs. The resulting image collection was compared with available historical photo identifications and databases using an automated image recognition algorithm. This approach yielded 36 years of photographic identification totaling 431 recaptures in Nicaragua (2006-2008 and 2016-2021) and 2539 recaptures (1986-2020) in both feeding and breeding grounds of 176 unique individuals sighted in Nicaragua. Our results showed that photo-identified whales were recaptured between October and April in breeding grounds and year-round in feeding grounds between British Columbia and California, with peak recaptures between June and October. Our study provided first-time evidence on fine-scale site affinity of individual humpback whales within Nicaraguan waters and to other breeding and feeding grounds.
Assuntos
Jubarte , Animais , Nicarágua , Melhoramento Vegetal , América Central , Algoritmos , CetáceosRESUMO
This study characterizes a decadal assessment of polycyclic aromatic hydrocarbons (PAHs) in the muscle tissues of mesopelagic fish species as indicators of the environmental health of the Gulf of Mexico (GoM) deep-pelagic ecosystem. Mesopelagic fishes were collected prior to the Deepwater Horizon (DWH) oil spill (2007), immediately post-spill (2010), 1 year after the spill (2011), and 5-6 years post-spill (2015-2016) to assess if the mesopelagic ecosystem was exposed to, and retained, PAH compounds from the DWH spill. Results indicated that a 7- to 10-fold increase in PAHs in fish muscle tissues occurred in 2010-2011 (4972 ± 1477 ng/g) compared to 2007 (630 ± 236 ng/g). In 2015-2016, PAH concentrations decreased close to the levels measured in 2007 samples (827 ± 138 ng/g); however, the composition of PAHs still resembles a petrogenic source similar to samples collected in 2010-2011. PAH composition in muscle samples indicated that natural sources (e.g., Mississippi River and natural seeps) or spatial variability within the GoM do not explain the temporal variability of PAHs observed from 2007 to 2016. Furthermore, analysis of different fish tissues indicated the dietary intake and maternal transfer of PAHs as the primary mechanisms for bioaccumulation in 2015-2016, explaining the elevated levels and composition of PAHs in ovarian eggs.
Assuntos
Poluição por Petróleo , Hidrocarbonetos Policíclicos Aromáticos , Poluentes Químicos da Água , Animais , Ecossistema , Monitoramento Ambiental , Peixes , Golfo do México , MississippiRESUMO
The blowout of the Deepwater Horizon (DWH) drill-rig produced a surface oil layer, dispersed micro-droplets throughout the water column, and sub-surface plumes. We measured stable carbon and nitrogen isotopes in mesopelagic fishes and shrimps in the vicinity of DWH collected prior to, six weeks after, and one year after the oil spill (2007, 2010 and 2011). In 2010, the year of the oil spill, a small but significant depletion of δ(13)C was found in two mesopelagic fishes (Gonostoma elongatum and Chauliodus sloani) and one shrimp (Systellaspis debilis); a significant δ(15)N enrichment was identified in the same shrimp and in three fish species (G. elongatum, Ceratoscopelus warmingii, and Lepidophanes guentheri). The δ(15)N change did not suggest a change of trophic level, but did indicate a change in diet. The data suggest that carbon from the Deepwater Horizon oil spill was incorporated into the mesopelagic food web of the Gulf of Mexico.