The Serra Spanish mackerel fishery (Scomberomorus brasiliensis – Teleostei) in Southern Brazil: the growing landings of a high trophic level resource

In fisheries, the phenomenon known as fishing down food webs is supposed to be a consequence of overfishing, which would be reflected in a reduction in the trophic level of landings. In such scenarios, the resilience of carnivorous, top predator species is particularly affected, making these resources the first to be depleted. The Serra Spanish mackerel, Scomberomorus brasiliensis, exemplifies a predator resource historically targeted by artisanal fisheries on the Brazilian coast. The present work analyzes landings in three periods within a 50-year timescale on the Parana coast, Southern Brazil, aiming to evaluate whether historical production has supposedly declined. Simultaneously, the diet was analyzed to confirm carnivorous habits and evaluate the trophic level in this region. Surprisingly, the results show that from the 1970’s to 2019 Serra Spanish mackerel production grew relatively to other resources, as well as in individual values. The trophic level was calculated as 4.238, similar to other Scomberomorus species, consisting of a case where landings increase over time, despite the high trophic level and large body size of the resource. The results agree with a recent global assessment that has demystified a necessary correlation between high trophic level and overexploitation, but possible factors acting on the present findings are discussed.

USE OF DISSOLVED ORGANIC MATTER BY MICROORGANISMS: FORMATION OF WATER QUALITY IN A POND OF A HIGH TROPHIC LEVEL

The role of algae and bacteria in the consumption and mineralization of dissolved organic matter (DOM) in a highly trophic aquatic ecosystem was studied. The phytoplankton and bacterioplankton community consumed 60% of added DOM in August and 56% of DOM in September. Of the uptaken DOM, a significant amount of organic carbon was mineralized. In August 42.7% and in September 29% of organic carbon (of the consumed organic matter) were used for respiration.

Kondisi plankton pada tambak ikan kerapu di Desa Mesjid Lama Kecamatan Talawi Kabupaten Batu Bara, Sumtera Utara

Fishpond is one of the habitats from organisme such as plankton which is have a role as main food resources for organisms with high trophic level (such as fish). This objectives of the study were to determine the condition of plankton in grouper fishponds in Mesjid Lama Village, Talawi District, Batu Bara District. Plankton sampling and water quality measurements were carried out from February to June 2019. The abundance of phytoplankton in grouper fish ponds varied between 1,765-4,113 ind/L. The composition of phytoplankton species found during observation was dominated by diatom groups or Bacillariophyceae classes. The abundance of zooplankton in grouper ponds varied from 330-1,165 ind/L with the lowest abundance found at station 6 with a total of 330 ind/L and the highest abundance was found at station 4 with a number of 1,165 ind/L. The zooplankton genus that is often found is Acartia. Diversity value H '

A temporal shift in trophic diversity among a predator assemblage in a warming Arctic

Climate change is leading to northward shifts in species distributions that is altering interspecific interactions at low- and mid-trophic levels. However, little attention has been focused on the effects of redistributions of species on the trophic ecology of a high trophic-level predator assemblage. Here, during a 22-year period (1990–2012) of increasing sea temperature (1.0°C) and decreasing sea ice extent (12%) in Cumberland Sound, Nunavut, Canada, we examined the trophic structure of a near-apex predator assemblage before (1990–2002) and after (2005–2012) an increase in the availability of capelin—generally an indicator species in colder marine environments for a warming climate. Stable isotopes (δ 13 C and δ 15 N) were used in a Bayesian framework to assess shifts in diet, niche size and community-wide metrics for beluga whales ( Delphinapterus leucas ), ringed seals ( Pusa hispida ), Greenland halibut ( Reinhardtius hippoglossoides ) and anadromous Arctic char ( Salvelinus alpinus ). After 2005, consumption of forage fish increased for all predator species, suggesting diet flexibility with changing abiotic and biotic conditions. An associated temporal shift from a trophically diverse to a trophically redundant predator assemblage occurred where predators now play similar trophic roles by consuming prey primarily from the pelagic energy pathway. Overall, these long-term ecological changes signify that trophic shifts of a high trophic-level predator assemblage associated with climate change have occurred in the Arctic food web.

Mangroves as Fish Habitat

Scientists have long sought to understand the contribution of mangrove forests to offshore systems, especially the movement of fishes from vegetated shallows to coral reefs (Parrish 1989). Typically, it is on coral reefs that fishing pressure is most intense (Stallings 2009). Previous studies focusing on mangrove-utilizing Caribbean fishes that migrate offshore with ontogeny have been restricted in spatiotemporal extent (e.g., Nagelkerken et al. 2002), and methodological and other differences among these research efforts have hindered quantitative, interstudy comparisons. Moreover, these studies did not directly account for (i.e., incorporate in their data analyses) the potentially confounding influence of human activity (i.e., fishing and/ or habitat degradation) when examining for relationships linking mangrove presence or area to fish abundance on reefs. As a result, it remains unclear whether island-scale observations consistent with mangrove-mediated augmentation of fishes on coral reefs are also evident at the scale of the greater Caribbean region. Human influence on large, high–trophic level Caribbean fishes appears strong (Stallings 2009); therefore, it is important to account for this influence when examining for a mangrove-driven fish subsidy effect at the regional scale.