Relationships Between Female Parent and Offspring Quality in Summer Flounder

All spawning biomass in a fish population is not equal.  Gamete quality is expected to vary among individual adults.  A critical feature of fisheries that are regulated by body size (total length) such as the summer flounder (Paralichthys dentatus) fishery is that the larger and presumably older fish are culled from the population.  These landed fish are more likely to be female, to be more fecund, and – if studies from other taxa are any indication – to produce offspring of higher quality than the remaining sub-legal size fish.  The goal of this work was to determine the existence and estimate the magnitude of relationships between the size and age of female summer flounder and the quality of their offspring.  We employed a two-pronged approach in our study that took advantage of data resources in NOAA Fisheries, Northeast Fisheries Science Center (NEFSC), and of the fish-rearing capabilities at the NEFSC Sandy Hook Laboratory.  Specifically, we first analyzed existing ichthyoplankton and adult trawl-survey data on summer flounder from the Mid-Atlantic region that have not yet been brought to bear on the question of female differences in offspring quality.  Those data show a clear seasonal progression with egg size increasing as spawning season advances.  This pattern was independent of latitude of capture.  Second, we conducted a series controlled laboratory experiments to directly quantify relationships between attributes of female parents (i.e., sizes and ages) and the quality of their offspring (e.g., sizes of eggs, hatchlings, and feeding larvae; developmental and survival rates of embryos and larvae).  We found significant correlations at the female (sib-group) level among the set of early life-stage features, and that egg size was predictive of sizes during the earliest life-stages.  From these relationships, we evaluate the consequences of maternal effects on offspring quality, including the role of time and location of spawning, and the possible consequences of a size-selective fishery.