Scientia Marina

Evidence of economic benefits from marine protected areas

Mark John Costello — 2024-03-27

Marine protected areas (MPAs) have been used for biodiversity conservation for decades. However, critics argue that evidence of their economic benefits is weak, particularly with regard to fisheries. This continued opposition to MPAs for fisheries slows progress towards conservation targets and undermines the economic and ecological sustainability of the oceans. This paper provides 48 examples of fishery-related and 31 of tourism-related economic benefits in 25 and 24 countries, respectively. There was no evidence of net costs of MPAs to fisheries anywhere. Fishery benefits included increased fish stocks, catch volumes, catch per unit effort, fecundity and larval export, and larger fish and lobsters. Well-designed and enforced MPAs provide sustainable benefits for fishing communities and even sub-optimally designed MPAs can provide economic advantages. MPAs represent one of the best strategies for maintaining the sustainable exploitation of marine resources.

Length-weight relationships of 15 mesopelagic shrimp species caught during exploratory surveys off the Canary Islands (central eastern Atlantic)

Airam Guerra-Marrero — 2024-02-28

Length-weight relationships (LWRs) were estimated for 15 mesopelagic shrimp species off the Canary Islands (central eastern Atlantic). Total length, cephalothorax length and total weight were taken for individuals collected during three research campaigns using a commercial semi-pelagic trawl net. The most represented families among the collected species were Sergestidae and Oplophoridae, with eight and three species, respectively. Overall, 60% of the species showed isometric growth, 33.3% negative allometry and 6.7% positive allometry. These 15 LWRs are the first contribution on mesopelagic shrimp species from the northwest Africa region, contributing to knowledge on the relative growth of these crustaceans.

Morphological and molecular evidence of cryptic speciation in sympatric colour morphotypes of Mycale (Carmia) cecilia (Porifera: Poecilosclerida) from the Mexican Pacific

Ana Castillo-Páez — 2024-03-15

Identifying cryptic species is pivotal for understanding marine biodiversity and optimizing strategies for its conservation. A robust understanding of poriferan diversity is a complex endeavour. It has also been extremely hampered by the high phenotypic plasticity and the limited number of diagnostic characters. Mycale (Carmia) cecilia has different body colours, even among individuals living together. We tested whether the colour variation could be due to polymorphism, phenotypic plasticity or cryptic speciation. Phylogenetic reconstructions of nuclear and mitochondrial loci were congruent. Individuals of different body colour did not cluster together and had high levels of genetic divergence. Furthermore, the green morphotype clustered in almost all reconstructions with Mycale (C.) phyllophila, as both showed higher gene similarity at the transcriptomic level (public transcriptome). Morphologically, the green individuals consistently showed discrepancies from the red ones. These results suggest that all individuals with the same body colour, either red or green, correspond to the same species, while individuals with different body colours probably belong to different species. These results reveal high levels of morphologic and genetic diversity, which could have important implications for what is known as M. (C.) cecilia and the Mycalidae systematics.

Enhancing the utility of known-biomass production models: a case study of the Bay of Biscay and Iberian Coast ecoregion

Mohamed Yosri Zanni — 2024-03-14

Our general purpose is to support the use of known-biomass production models (KBPMs), illustrating their usefulness by addressing the evolution of surplus production (SP) over time and the factors affecting it (e.g. environment). We also demonstrate the utility of KBPMs for multispecies management objectives or for estimating maximum sustainable yield reference points without a stock recruitment function, among other worthwhile applications. To do so, we present different uses of KBPMs, illustrating their application on demersal species in the International Council for the Exploration of the Sea (ICES) area, specifically for megrim, white anglerfish and European hake stocks. The proposed analytical approach involved fitting single-species and multispecies KBPMs, conducting retrospective analyses and assessing the effects of environmental variability on SP. The findings show that, in general, stock SP increased after a decline in biomass and SP, except for white anglerfish in the southern area. Megrim stocks are the least productive, while hake and northern anglerfish are the most productive. Retrospective analysis revealed SP shifts in northern hake stock for reasons other than biomass variability. Hence, the North Atlantic Oscillation and the Atlantic Multidecadal Oscillation (AMO), two key climate variability modes in the North Atlantic, were tested for their links to SP, revealing a positive connection between SP and AMO, although further research is necessary. Beyond the specific results of our particular KBPM application, our main conclusion is that KBPMs can serve as a tool complementary to more complex assessment models for resolving unaddressed issues and crosschecking available assessment results.