Thassya C. dos Santos Schmidt

Marine and Freshwater Research Institute | MRI · Pelagic Group

Atlantic herring (Clupea harengus) has a complex population structure and displays a variety of reproductive strategies. Differences in reproductive strategies among herring populations are linked to their time of spawning, as well as to their reproductive investment which can be an indicator for migratory vs. stationary behavior. These differences...

The oocyte development (vitellogenesis) of individual fish is highly dependent upon their physiology which is influenced by both intrinsic and extrinsic factors. Thus, if individuals encounter poor biophysical conditions, they will likely be unable to reproduce. The photoperiod is an external factor that is constant between years but with increasin...

The present study tracked oocyte development over 9 months and noted incidences of ‘skipping’, i.e. adults terminating their upcoming reproductive cycle, in field‐caught Northeast Arctic (NEA) haddock (Melanogrammus aeglefinus), currently the largest stock of this species. Applications of advanced image and histological techniques revealed the pres...

The understanding of teleost fecundity type (determinate or indeterminate) is essential when deciding which egg production method should be applied to ultimately estimate spawning stock biomass. The fecundity type is, however, unknown or controversial for several commercial stocks, including the Northeast Atlantic mackerel (Scomber scombrus). Aimin...

Summary of research, by all vessels, which participated in the International Ecosystem Summer Survey in July 2021.

The International Ecosystem Summer Survey in the Nordic Seas (IESSNS) was performed within approximately 5 weeks from June 30th to August 3rd in 2021 using five vessels from Norway (2), Iceland (1), Faroe Islands (1) and Denmark (1). The main objective is to provide annual age-segregated abundance index, with an uncertainty estimate, for northeast...

Life-history traits of Pacific (Clupea pallasii) and Atlantic (Clupea harengus) herring, comprising both local and oceanic stocks subdivided into summer-autumn and spring spawners, were extensively reviewed. The main parameters investigated were body growth, condition, and reproductive investment. Body size of Pacific herring increased with increas...

Egg surveys are used worldwide for the estimation of spawning stock biomass (SSB) of small pelagic fish species, requiring detailed knowledge about their reproductive biology. In the present study, we revisit the current conceptual framework of teleost fecundity types using Northeast Atlantic (NEA) mackerel (Scomber scombrus) as case study due to c...

We analyzed ovarian dynamics of anadromous blueback herring, Alosa aestivalis, in Connecticut River with the principal aim of exploring oocyte recruitment and how it shapes the fecundity pattern. We examined the oocyte release strategy and analyzed spawning cyclicity by linking oocyte growth to the degeneration of postovulatory follicles. Females w...

Reproductive investment is a central trait for population dynamics and productivity. Fishing and environmental variations are major drivers affecting population structure, dynamics, and adaptation of life-history and behavioural traits. However, those factors are often considered independently, and few studies take into account their joint effect....

The collection and presentation of accurate reproductive data from wild fish has historically been somewhat problematic, especially for serially spawning species. Therefore, the aim of the current study was to develop a novel method of assessing female spawning status that is robust to variation in oocyte dynamics between specimens. Atlantic cod (B...

Here we challenge traditional views on the direction of change in teleost body condition and reproductive traits in response to abiotic and biotic factors by studying the data-rich, planktivorous Norwegian spring-spawning herring (NSSH), a member of the abundant Atlantic herring (Clupea harengus) stock complex. To test potential influential factors...

It is well known that marine fish dynamics relate with climate variability, and predicting future population developments have become increasingly urgent with on-going climate change. One approach in widespread populations is to study how individuals from different parts of the distribution area respond to climate, thereby testing for potential res...

The aim of this study was to investigate the ichthyofauna structure in the region of the north outfall of the Bertioga Channel (São Paulo, Brazil) and the possible effects of the environmental quality loss. The samples were collected in a monthly basis, from September to December 2005, at two oceanographic stations with an otter-trawl. The fish fau...

Significance Fish stock advice and management have a focus on protecting the reproductive capacity of a stock. Central to the associated research undertaken is whether spawning stock biomass is a proxy for total egg production. Here we demonstrate for the planktivorous Atlantic herring that the standard use of season-independent potential fecundity...

Herring from two unexploited fjord populations, Lake Rossfjord (LRH, n = 100) and Balsfjord (BFH, n = 420) in northern Norway, were sampled in 2014 and 2015. Life history characteristics were analysed and compared to the oceanic Norwegian spring-spawning herring (NSSH), and other Atlantic and Pacific herring stocks. Genetic studies have shown that...

The a and b parameters of the length-weight relationship (LWR) of the form W = aL(b) were estimated for 71 species of Actinopterygii and 2 Elasmobranchii, caught in the coastal region and inner shelf of southeastern Brazil. Estimates of b varied from 2.151 to 3.882. For the first time LWR for eight fish species is reported. Significant differences...

The a and b parameters of the length-weight relationship (LWR) of the form W = aLb were estimated for 71 species of Actinopterygii and 2 Elasmobranchii, caught in the coastal region and inner shelf of southeastern Brazil. Estimates of b varied from 2.151 to 3.882. For the first time LWR for eight fish species is reported. Significant differences we...

The Sciaenids have among the highest species richness, numerical abundance and biomass of any family of fishes along the Brazilian coast. The aim of this study was to analyze the composition and spatial and temporal distribution of as well as the influence of temperature, salinity and depth on the sciaenid assemblage of Santos Bay. A total of 29,30...

The community structure and dynamics as well as some biological parameters of selected species of the ichthyofauna of the Mataripe estuarine region affected by the Landulfo Alves Oil Refinery (RLAM) were analyzed. Twenty stations were sampled with a gillnet in five different periods: August and December 2003, March and July/August 2004 and January...

O objetivo do trabalho foi analisar a taxocenose de bagres marinhos do complexo baía-estuário de São Vicente, SP. As coletas foram mensais, no período de setembro de 2000 a agosto de 2002, em quatro regiões do estuário. Foram capturados 3.985 exemplares, pertencentes a cinco gêneros e seis espécies, totalizando 47.807 g. A espécie Cathorops spixii...

The purpose of this study was to analyze the taxocenose of marine catfish in the complex bay-estuary of Sao Vicente, Brazil. The sampling was done monthly from September/2000 to August/2002, in four places of the estuary. Were caught 3.985 individuals belonging for 5 genus and 6 species, totalizing 47.807 g. The specie Cathorops spixii showed the b...