Human impacts on fisheries across the land–sea interface

Abstract

A long-held paradigm is that estuaries are important to the welfare of estuarine-dependent coastal fisheries, providing spawning areas, suitable salinity gradients for development, protection from predators, and food. Many publications link the beneficial nature of estuaries with fisheries production and decry human activities that modify habitat, and therefore potentially decrease fisheries production. However, what if the water quality of the estuary, often human-driven, results in less than suitable habitat for coastal fisheries productivity, both in the estuary and in the adjacent offshore waters? Finding the data to support relationships (positive and negative) among estuaries and coastal fisheries production is difficult because of inadequate data, highly variable data, or data with no clear linkages to processes. Hughes et al. (1), however, amassed a dense and multifaceted database of declining estuarine water quality in the form of worsening hypoxia to declines of fish diversity, reduced estuarine habitat suitability, and declines in offshore fisheries. The authors defend a plausible mechanism across the landsea interface.Relationships among hypoxic waters and fisheries productivity (either catch per unit effort or landings) remain as elusive as relationships of nitrogen loading and fisheries productivity. Efforts to understand these ocean trophic models shifted over the 20th century from agricultural models of food stimulated by nutrients that feed higher primary producer standing stocks and secondary production to concerns of higher N and P loads into water bodies, excess phytoplankton biomass, and the deleterious effects of eutrophication, including harmful algal blooms and hypoxia ( Fig. 1) (2-6).A meta-analysis by Micheli (7) of 47 food webs (natural and experimental) verified a relationship between nitrogen loading and primary production but not necessarily standing stocks of secondary consumers in the form of fisheries. Breitburg et al. (8) followed with a broad global analysis of 30 estuaries and semienclosed seas and found few strong relationships between N loading and fisheries production and hypoxia and fisheries production. Their divisions for fisheries were pelagic planktivores, benthopelagics, and benthics. Fisheries landings were positively related to N loading only for the benthopelagics and pelagics. None were related to the percent of the bottom water that was hypoxic.On more local or regional scales, however, there are documented decreases in landings or catch per unit effort with increase in area of hypoxia. Cod landings in the Baltic decline with an increase in stratification that affects the buoyancy of cod eggs so that they do not reach suitable habitat for development and with an increase in volume of hypoxic bottom-water that negatively affects survivability (9, 10). A similar decrease in cod landings in the western Atlantic is potentially related to increasing nutrient loads in the St. Lawrence River estuary and subsequent hypoxia (11,12).The bottom-waters of the northern Gulf o...

Conflicts in the coastal zone: human impacts on commercially important fish species utilizing coastal habitat

“…Relevant keywords used in search Toxicants and Pollutants "xenobiotics" or "toxic* or "sewage" or "contaminant" or "pollution" Eutrophication and Anoxia "eutrophication" or "hypoxia" Invasive Species "invasi*" or "outbreak" or "proliferation" Physical Coastal Development "land reclamation" or "sediment" or "habitat loss" or "extraction" or "depth change" Indirect Fishing Impacts "fishing" or "trawling" or "dredging" Continued higher nutrient loads may negatively impact fish populations by decreasing the cover of canopy forming vegetation (Cloern, 2001) and increasing the frequency of anoxic events (Rabalais, 2015), in turn causing increases in the mortality of early life-history stages and reducing growth rates in fish (Kornilovs, 1993;Petersen and Pihl, 1995;Maes et al, 2007;Teschner et al, 2010). In addition to the widely known direct effects of fishing on fish species, this study found that fishing often indirectly impacted fish through the destruction of biogenic structures which provide shelter (Hall-Spencer et al, 2003;Kamenos et al, 2004).…”

“…In terms of physical perturbations, destructive fishing methods such as bottom trawling also disrupt important fish habitats (Hiddink et al, 2006). Simultaneously, degradation of coastal fish habitats can also be brought about through eutrophication and subsequent macroalgal blooms (Rabalais, 2015;Le Luherne et al, 2016) or anoxic events (Cloern, 2001) derived from nutrient input associated with urban and agricultural activities. Other terrestrial and coastal activities (e.g.…”

Direct ingestion, trophic transfer, and physiological effects of microplastics in the early life stages of Centropristis striata, a commercially and recreationally valuable fishery species

“…This species feeds opportunistically upon a variety of prey items and thus accidental ingestion of microplastics from the water column as the fish mistakes plastic for prey is a potential concern (Sedberry 1988;Devriese et al 2015). C. striata utilize nursery habitats in estuaries and coastal waters that are notably impacted by anthropogenic activities, during their early life stages (Beck et al 2001;Rabalais 2015;Vendel et al 2017). Interspecific variation in microplastics ingestion is likely due to the species-specific feeding strategies and abundance of plastics in their surrounding environment (Lusher et al 2013, de Ruijter et al 2020.…”

Using a spatially structured life cycle model to assess the influence of multiple stressors on an exploited coastal-nursery-dependent population

“…However, life cycle approaches integrating impacts of these multiple stressors all along the life cycle remain rare. Also, less attention has been paid to the quantitative assessment of how the spatial structure of populations and patterns of connectivity along the life cycle interact with spatially structured stressors (Cianelli et al, 2013) such as coastal nursery habitat degradation (Rabalais, 2015) or spatially non-homogenous fishing effort.…”