Abstract This study presents the first record of the cordiform echinoid Plagiobrissus grandis (Gmelin, 1791) (Echinoidea: Spatangoida: Brissidae) in Paraná’s shallow inner shelf, in addition to a brief description of its location, body measurements, sex determination, and reproductive status. Two specimens were recorded between 2015 (bycatch by artisanal fishing) and 2016 (observed by scuba diving). The only specimen - with severe signs of weakness - captured was donated to Associação MarBrasil and kept in an aquarium for rehabilitation (8 days), where it was possible to observe digging movements, burying skills (partially), and camouflage or covering behavior. The organism was sent to the UNESPAR campus of Paranaguá and was photographed, measured (length: 155.65 mm, width: 118.93 mm, and maximum test height: 41.31 mm), fixed, and properly preserved. Digitized images of the histological preparation showed that it was a female in the recovery stage (or nutritional reserve) of the reproductive cycle. Regardless of their limitations, the current records for the Brissidae family in South Atlantic are still concentrated on the Brazilian coast, contributing to the understanding of zoogeographic, ecological, morphophysiological, and behavioral aspects of the spatangoid echinoids.

Scallops were collected from beds at 30 to 40 m depth on the south-southern inner continental shelf of Brazil for histological gonadal characterization of the reproductive cycle. This hermaphroditic scallop was an important shellfish resource during 70-80 decade, with maximal annual landings of 8,845 tons, but now is depleted. Results shows that reproduction is continuous, with two major spawning periods, the first during end of summer and throughout autumn, and the second during winter and beginning of spring. A characteristic phenomenon of oocyte atresia, with maximal incidences in September is described. This phenomenon, followed by the mature oocyte resorption and new oocyte proliferation and maturation, was related to the lack of spawning stimulation. A semi-annual thermal cycle on the bottom water due to the South Atlantic Central Water intrusion seems to be the principal reproductive cycle controller. Fluctuations in landings registered since the beginning of the fishery may be partly related to oceanographic variations.

Material collected with a 2-meter wide beam trawl during eight surveys conducted from December 1995 to February 1997 was used for a first preliminary description of the reproduction and population dynamics of the edible venerid bivalve Chione pubera (Bory Saint-Vicent, 1827). Greatest catches were found between 30 to 35 meters depth, on fine sandy bottoms with a mud content lower than 10%. Dry weight meat condition index showed highest values during autumn and lowest values from winter to summer months. Histological analysis of gonadal tissue showed a continuous reproduction, with peaks of maturation on autumn and spring, Spawning was related with the increase of water temperature, that occurs twice a year in the region as a consequence of a particular hydrological characteristic of the inner continental shelf. Size frequency distribution showed a unique principal mode with slow if any displacement through time, indicating a long lived species.