Description

Understanding animals' reproductive output is essential for comprehending their life history and assessing their reproductive success. For figuring out a species' reproductive life history, fishes' clutch size, egg size, relative clutch mass, spawning interval, gonadosomatic index, and length of the reproductive season are important parameters. In the study of life history evolution and in comprehending traits' adaptability to environmental conditions, which are becoming ever more important with environmental change and interest in conserving biodiversity, the precise determination of these reproductive parameters is critical. Furthermore, researchers can benefit from the collective efforts of the scientific community by making broad comparisons based on small-scale individual studies using precise techniques.

Macroscopic and histological ovarian terminology were initially developed for commercially important marine fishes. defined a number of oocytes in the Pacific Sardine (Sardinops sagax caerulea)'s various macroscopic stages; Several scientists who worked with freshwater fishes later adopted these definitions. When developing macroscopic descriptions of ovaries, biologists studying small freshwater fish typically adapted terminology developed for larger, commercially important species. Based on various perspectives of the oocyte development, ovum maturation, and oviposition processes, a variety of approaches to the study of reproduction emerged. In a similar vein, the terms utilized in various studies to describe the macroscopic development of small marine fishes have varied. As a consequence of this, the data that are produced by various authors to describe comparable reproductive parameters vary significantly, leading to confusion and unreliability among studies. In an effort to standardize the methodology and terminology used to describe reproduction in small freshwater fishes, macroscopic images of ovarian development and the terminology that goes along with them were created around 1993.

Oocyte Development and Ovum Maturation

A new scale based on macroscopic and histological terminology related to important African and Neotropical fauna was also developed to clear up the confusion, but this terminology has not been widely used in the fish literature. Until the development of standardized terminology based on histological descriptions became widely used in the literature, terms used to describe ovarian development and reproductive seasonality in marine fishes were similarly ambiguous.

Based on the stages of oocyte development and maturation, a review of macroscopic and histological methods for evaluating ovarian reproduction phases is provided here. For macroscopic descriptions of small freshwater fishes, we propose a hybrid approach that combines both histological and macroscopic approaches and demonstrates their complementarity. Based on a combination of recent studies of small freshwater and marine fishes, a proposal for standard terminology to describe oocytes and ovarian processes is included. These studies can be applied to small marine fishes with similar reproductive strategies and have important implications for various methods used to study life history traits, particularly for small freshwater fishes. Based on published results from a variety of fish species, the methods described here represent a strategy that will provide accurate and comparable data for subsequent studies of reproduction. In particular, they make it possible to accurately describe and classify ovaries prior to ovulation and spawning, which is crucial. The descriptions in this paper are solely based on preserved ovaries because researchers typically work with preserved specimens.

Macroscopically or histologically, gamete cells in distinct stages can be observed in the ovaries of sexually mature females during the spawning season. Depending on her reproductive stage, any female may exhibit some or all of these cellular stages.

Catches of Small Pelagic Fishes

Authors have used a variety of names to describe the gamete cells in fish ovaries. When performing a macroscopic assessment, it is common practice to refer to all of the cells as "ova" or "eggs" and to use adjectives to differentiate between them, such as "immature ova" and "mature ova." Histological studies, on the other hand, typically refer to female gametes as "oocytes." This terminology needs to be changed to provide a more comprehensive, refined, and consistent nomenclature in order to make it possible to conduct studies of reproductive biology with greater precision.

Both the assignment of ovarian phases and the microscopic staging of oocyte development and maturation have frequently been closely intertwined, and the terminology used to describe each phenomenon has frequently been very similar based on the stage of the most advanced oocytes. The size, transparency, translucence, opacity, and color of the ovaries and oocytes, in addition to their location within the follicles or lumens of the ovaries, serve as the basis for the criteria. The cytoplasm of the smallest cells, which appear to be latent, is typically transparent or slightly translucent, and the large nuclei are easily visible. With the nucleus obscured by cytoplasmic inclusions that cause the oocytes to become translucent and opaque white, the active development of oocytes can be seen in cells that have grown in size. Oocytes that are growing in size typically change color from white to cream and yellow in order. Depending on whether they are finishing oocyte development (i.e., loading vitellogenin) or going through oocyte maturation, the largest follicular cells will look very different from one female to the next. They could be a dark or opaque yellow. Oocytes may be translucent, transparent, yellow, amber, or even orange in cases of advanced development leading to oocyte maturation. Oocytes that are still in follicles and are considered to be ripening will typically have elevated vitelline membranes and be translucent to transparent in part due to hydration. Oocytes at ovulation, also known as ripe eggs, have the same characteristics as ripening oocytes; However, they can be found in the ovaries' lumens.

In 2015, 2016, and 2017, trained WDFW fisheries technicians who were also experienced salmon anglers were employed to fish the Nisqually and Puyallup rivers from shore using standard drift and BUB techniques to describe the hooking location on fish landed across various leader lengths. Anglers were provided with three pre-made 20-pound leaders when fishing with drift fishing equipment. strength (test) constructed using a barbless hook of size 1/0.