scholarly journals Stock collapse and its effect on species interactions: Cod and herring in the Norwegian‐Barents Seas system as an example

2021 ◽  
Author(s):  
Joël M. Durant ◽  
Leana Aarvold ◽  
Øystein Langangen
Keyword(s):  
Species Interactions ◽  
Stock Collapse

scholarly journals Stock collapse and its effect on species interactions: cod and herring in the Norwegian-Barents Seas system as an example

2021 ◽  
Author(s):  
Joel Durant ◽  
Leana Aarvold ◽  
Øystein Langangen
Keyword(s):  
Population Dynamics ◽  
Species Interactions ◽  
Gadus Morhua ◽  
Barents Sea ◽  
Biotic Interactions ◽  
Clupea Harengus ◽  
Late 20Th Century ◽  
Before And After ◽  
The Difference ◽  
Stock Collapse

Both the Norwegian Spring Spawning herring (Clupea harengus) and the Northeast Arctic cod (Gadus morhua) are examples of how the overexploitation of marine fish populations was leading to a strong reduction even so stock collapse, with a strong decline in the associated fisheries, followed by a recovery. Cod and herring are both part of the Barents Sea ecosystem, which experienced major warming events in the early (1920-1940) and late 20th century. While the collapse or near collapse of these stocks seems to be linked to instability created by overfishing and climate, the difference of population dynamics before and after is not fully understood. In particular, it is unclear how the changes in population dynamics before and after the collapses are associated with biotic interactions. The combination of the availability of unique long-term time series for herring and cod makes it a well-suited study system to investigate the effects of collapse. We examine how species interactions may differently affect the herring and cod population dynamic before and after a collapse. Particularly we explore, using a GAM modelling approach, how herring could affect cod and reciprocally. We found that the effect on herring of cod biomass that was generally positive (i.e., covariation) became negative after the collapse (i.e., predation or competition). Likewise a change occurred for the cod, the juvenile herring biomass that had no effect before the collapse had a negative one after. Our results indicate that population collapses may lead to altered inter-specific interactions as well as altered response to abiotic environmental variations. While the stocks are at similar abundance levels before and after the collapses the system is potentially different in its functioning and may require different management action.

Effects of marine reserves on predator-prey interactions in central California kelp forests

2020 ◽  
Vol 655 ◽  
pp. 139-155
Author(s):  
DC Yates ◽  
SI Lonhart ◽  
SL Hamilton
Keyword(s):  
Species Interactions ◽  
Size Structure ◽  
Marine Reserves ◽  
Mortality Rates ◽  
Kelp Forests ◽  
Negative Effects ◽  
Central California ◽  
Invertebrate Predators ◽  
Predatory Fishes ◽  
Density And Biomass

Marine reserves are often designed to increase density, biomass, size structure, and biodiversity by prohibiting extractive activities. However, the recovery of predators following the establishment of marine reserves and the consequent cessation of fishing may have indirect negative effects on prey populations by increasing prey mortality. We coupled field surveys with empirical predation assays (i.e. tethering experiments) inside and outside of 3 no-take marine reserves in kelp forests along the central California coast to quantify the strength of interactions between predatory fishes and their crustacean prey. Results indicated elevated densities and biomass of invertebrate predators inside marine reserves compared to nearby fished sites, but no significant differences in prey densities. The increased abundance of predators inside marine reserves translated to a significant increase in mortality of 2 species of decapod crustaceans, the dock shrimp Pandalus danae and the cryptic kelp crab Pugettia richii, in tethering experiments. Shrimp mortality rates were 4.6 times greater, while crab mortality rates were 7 times greater inside reserves. For both prey species, the time to 50% mortality was negatively associated with the density and biomass of invertebrate predators (i.e. higher mortality rates where predators were more abundant). Video analyses indicated that macro-invertivore fishes arrived 2 times faster to tethering arrays at sites inside marine reserves and began attacking tethered prey more rapidly. The results indicate that marine reserves can have direct and indirect effects on predators and their prey, respectively, and highlight the importance of considering species interactions in making management decisions.

Are local losses of biodiversity causing degraded ecosystem function?

2017 ◽  
Author(s):  
Mark Vellend
Keyword(s):  
Ecosystem Function ◽  
Species Interactions ◽  
Regional Scale ◽  
Temporal Trends ◽  
Biodiversity Loss ◽  
Large Degree ◽  
Global Scale ◽  
Degraded Ecosystem ◽  
Biodiversity Change ◽  
Local Extirpation

This chapter highlights the scale dependence of biodiversity change over time and its consequences for arguments about the instrumental value of biodiversity. While biodiversity is in decline on a global scale, the temporal trends on regional and local scales include cases of biodiversity increase, no change, and decline. Environmental change, anthropogenic or otherwise, causes both local extirpation and colonization of species, and thus turnover in species composition, but not necessarily declines in biodiversity. In some situations, such as plants at the regional scale, human-mediated colonizations have greatly outnumbered extinctions, thus causing a marked increase in species richness. Since the potential influence of biodiversity on ecosystem function and services is mediated to a large degree by local or neighborhood species interactions, these results challenge the generality of the argument that biodiversity loss is putting at risk the ecosystem service benefits people receive from nature.

scholarly journals Functional traits shape small mammal-helminth network: patterns and processes in species interactions

Parasitology ◽  
2021 ◽  
pp. 1-36
Author(s):  
Thiago dos Santos Cardoso ◽  
Cecilia Siliansky de Andreazzi ◽  
Arnaldo Maldonado Junior ◽  
Rosana Gentile
Keyword(s):  
Functional Traits ◽  
Small Mammal ◽  
Species Interactions ◽  
Patterns And Processes ◽  
Network Patterns
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