Life History Through the Eyes of a Hogfish: Evidence of Trophic Growth and Differential Juvenile Habitat Use

Understanding ontogenetic linkages among fish habitats is critical for conservation of fish populations and the ecosystems on which they rely. Natural tags such as stable isotopes are an effective tool commonly used to investigate ecological questions regarding fish movement and habitat use. Here, I analyzed stable isotopes from the sequentially deposited laminae of Hogfish (Lachnolaimus maximus) eye lenses from the eastern Gulf of Mexico (eGOM) to investigate trophic and geographic changes across individual life histories. I documented evidence of entire-life scale trophic growth through increases in δ15N. I also observed depth separation at the juvenile stage, evidenced by variation in δ13C. These results suggest that Hogfish inhabiting deeper adult habitats likely inhabited deeper juvenile habitats (i.e., nearshore reefs), while adult Hogfish inhabiting shallower adult habitats likely used shallower juvenile habitats (i.e., estuaries). This is a novel finding for eGOM Hogfish and contradicts prior literature that solely discuss seagrass as juvenile Hogfish habitat. A linear discriminant function analysis revealed the Cedar Key region to be the most highly used juvenile habitat by the Hogfish sampled in this study, but more evidence is needed to determine the status of this area as a Hogfish nursery. This study provides the first evidence for ontogenetic migration of individual Hogfish using natural tags as tracers and demonstrates a mechanism for identifying juvenile habitats based on eye lens stable isotope analysis. Identifying ontogenetic patterns and habitat use in Hogfish can help to better manage the stock and preserve essential habitats

Life History through the Eyes of a Hogfish: Trophic Growth and Differential Juvenile Habitat Use from Stable Isotope Analysis

Understanding ontogenetic linkages among fish habitats is critical for conservation of fish populations and the ecosystems on which they rely. Natural tags such as stable isotopes are effective for investigating ecological questions regarding fish movement and habitat use. We analyzed stable isotopes from sequentially deposited laminae of hogfish Lachnolaimus maximus eye lenses from the eastern Gulf of Mexico (eGOM) to investigate trophic and geographic changes across individual life histories. We documented evidence of 1 to 2 step trophic level increases through δ15N increases. We also observed depth separation at the juvenile stage, evidenced by δ13C variation early in life. These results suggest that adult hogfish in deeper habitats likely inhabited deeper juvenile habitats (i.e. nearshore reefs), while adult hogfish inhabiting shallower adult habitats likely used shallower juvenile habitats (i.e. estuaries). This novel finding for eGOM hogfish contradicts prior literature that solely discusses seagrass as juvenile habitat. We used muscle tissue isotopes to characterize juvenile hogfish habitats and linear discriminant function analysis (LDA) to determine the habitats previously inhabited by adults in this study. The LDA revealed Cedar Key as the most used juvenile hogfish habitat in this study, but more evidence is needed to determine its status as a nursery. This study provides the first evidence for ontogenetic migration of individual hogfish using natural tags as tracers and demonstrates a mechanism for identifying juvenile habitats based on eye lens stable isotope analysis. Identifying ontogenetic patterns and habitat use can help to better conserve stocks and essential fish habitats

Population Dynamics of Pinfish in the Eastern Gulf of Mexico (1998-2016)

Forage fishes play an important role in marine ecosystems by transferring energy and nutrients through the food web. The population dynamics of forage species can therefore have cascading effects across multiple trophic levels. Here, we analyzed a 19-year dataset on Pinfish (Lagodon rhomboides) across four eastern Gulf of Mexico estuaries to investigate population dynamics, inter- and intra-annual synchrony, metapopulation portfolio effects, growth, and habitat effects. Young-of-year growth rates did not differ among estuaries. The population dynamics of these four systems were stable in the long-term, but highly dynamic inter-annually. Intra-annual dynamics were stable and predictable despite variation in long-term means. Some estuaries exhibited positive inter-annual synchrony, and all four estuaries were synchronous intra-annually. There was evidence for stronger portfolio effects for the entire four-estuary metapopulation, as well as for the two northern estuaries while the southern estuaries appeared to act as a single population. Submerged aquatic vegetation was by far the most important predictor for both presence and abundance of Pinfish. It is important to understand the factors driving forage fish population fluctuations to better predict ecosystem effects, including those to species of economic and ecological importance. These predictors can be useful for the implementation of ecosystem-based management decisions

Global COVID-19 lockdown highlights humans as both threats and custodians of the environment

The global lockdown to mitigate COVID-19 pandemic health risks has altered human interactions with nature. Here, we report immediate impacts of changes in human activities on wildlife and environmental threats during the early lockdown months of 2020, based on 877 qualitative reports and 332 quantitative assessments from 89 different studies. Hundreds of reports of unusual species observations from around the world suggest that animals quickly responded to the reductions in human presence. However, negative effects of lockdown on conservation also emerged, as confinement resulted in some park officials being unable to perform conservation, restoration and enforcement tasks, resulting in local increases in illegal activities such as hunting. Overall, there is a complex mixture of positive and negative effects of the pandemic lockdown on nature, all of which have the potential to lead to cascading responses which in turn impact wildlife and nature conservation. While the net effect of the lockdown will need to be assessed over years as data becomes available and persistent effects emerge, immediate responses were detected across the world. Thus initial qualitative and quantitative data arising from this serendipitous global quasi-experimental perturbation highlights the dual role that humans play in threatening and protecting species and ecosystems. Pathways to favorably tilt this delicate balance include reducing impacts and increasing conservation effectiveness