An ecosystem modelling approach to deriving viable harvest strategies for multispecies management of the Northern Gulf of California

Abstract

ABSTRACT1. An ecosystem analysis was developed focusing on resource exploitation and biodiversity conservation for the Northern Gulf of California. The main tools employed were a trophic ecosystem model and time dynamic simulations.2. The ecosystem was represented by an Ecopath model that included 34 functional groups, from primary producers to top predators. It included relevant species in the area such as commercially important shrimp (e.g. Litopenaeus stylirostris) and highly endangered species (Phocoena sinus and Totoaba macdonaldi).3. Temporal simulations of changing fishing effort allowed the evaluation of fishing impact on the ecosystem components and, particularly, on protected species. Formal optimization methods were applied with the purpose of searching viable temporal patterns of fishing effort that might minimize social, economic and conservationist conflicts in the area.4. The results of those simulations showed the capability of the model to represent reference temporal series of relative biomass. The search for viable fishing strategies resulted in effort allocation consistent with those proposed by other studies; that is, a decrease in the industrial shrimp fleet (35-65%), a decrease in the gillnet fishing fleet (52-57%), and an increase of the artisanal shrimp fishery (63-222%).5. The main conflicts in the Northern Gulf of California seem to take place between social and conservation interests, while the economic and ecological benefits seem to be relatively independent. The next steps towards conflict resolution and ecosystem management should consider the design and operation of MPAs already established in the region.

Colorado River flow and biological productivity in the Northern Gulf of California, Mexico

“…There have been several attempts to model the ecosystem of the Northern Gulf, mainly using the Ecopath modeling software (Morales-Zárate et al 2004, Lercari 2006, Lercari and Arreguín-Sánchez 2009. These have concluded that reducing fishing pressure would increase fisheries stocks and reduce the risk to endangered species such as totoaba (Totoaba macdonaldi) and vaquita porpoise (Phocoena sinus).…”

“…These have concluded that reducing fishing pressure would increase fisheries stocks and reduce the risk to endangered species such as totoaba (Totoaba macdonaldi) and vaquita porpoise (Phocoena sinus). Lercari and Arreguín-Sánchez (2009) built an ecosystem model for the Northern Gulf that suggested a viable fishing strategy to protect totoaba and vaquita required a decrease in the industrial shrimp fleet (35-65%), a decrease in the gillnet fleet (52-57%), and an increase of the artisanal shrimp fishery (63-222%) if appropriate fishing methods were to be employed. Morales-Zárate et al (2004) compared their Northern Gulf model to five other coastal models in Mexico, suggesting a "higher energy use" in the Northern Gulf ecosystem, and that the region has a "highly dynamic, more complex, and probably a more mature ecosystem" than the others.…”

Brown Pelicans, Pelecanus occidentalis californicus (Aves: Pelecanidae): Five decades with ENSO, dynamic nesting, and contemporary breeding status in the Gulf of California

“…Although oceanic boundaries are variable and dynamic and some biological connectivity is high in the entire Gulf (Turk-Boyer et al 2014), San Luis and Cholluda Islands and other nearby pelican nesting islands (e.g., Puerto Refugio) are likely within a somewhat distinct ecosystem, variably defined as the "northern Gulf" (e.g., Hendrickson 1973;Maluf 1983;Santamaria-del-Angel et al 1994;Álvarez-Borrego 2002Álvarez-Borrego , 2003Findley 2007, 2010;Lercari and Arreguín-Sánchez 2008;Cisneros-Mata 2010; see also reviews by Herrera-Cervantes et al 2007 andPáez-Osuna et al 2016). Northern Gulf uniqueness is likely related to high tidal influences and other more local features, remaining still productive offshore in the northern Gulf despite extreme changes farther up in the Colorado River delta area (Álvarez-Borrego 2002(Álvarez-Borrego , 2003Ramírez-León et al 2015;Brusca et al 2017).…”

Ecological singularity of temperate mesopredatory myliobatoid rays (Chondrichthyes: Myliobatiformes)

“…Myliobatoid mesopredators are often pooled together in analyses of trophic webs, especially for regions with low diversity (e.g. Arreguín-Sánchez et al 2002;Gasalla and Rossi-Wongtschowski 2004;Barausse et al 2009;Lercari and Arreguín-Sánchez 2009;Ruiz and Wolff 2011). Unless there is evidence of ecological redundancy among myliobatoid mesopredators of a given region, as found by O' Shea et al (2013), the results of the present study indicate that the practice of pooling together all myliobatoid mesopredators should be abandoned.…”