Optimizing biological parameterization in the egg escapement model of the market squid, (Dorytheuthis opalescens), population off California.
Creators: name: McDaniel, Jenny
name: Dorval, Emmanis
name: Taylor, Julianne
name: Porzio, Dianna
Publisher: name: U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Southwest Fisheries Science Center
Year: 2015
Subjects: subject: Loligo opalescens--Estimates--California--Mathematical models.

description: Over the last two decades, the market squid (Doryteuthis opalescens) fishery has been one of the most productive and valuable fisheries off California. In 2005, the California Department of Fish and Wildlife (CDFW) established a management plan including fishery controls rules with a seasonal catch limitation and a weekend closure of the fishery. In the absence of adequate information to establish a maximum sustainable yield (MSY), the egg escapement method was identified as the best available tool to provide a proxy for maximum sustainable yield/optimum yield (MSY/OY). However, recent published studies identified laboratory processing time as a critical area of concern for the successful application of the egg escapement method. The original laboratory and field protocols required squid mantle tissue to be dried for 14 days at 56°C and female squid gonads to be preserved in 10% neutral buffered formalin and weighed at a later date. These methods led to a significant lag between the time of sample collection and the availability of data needed to apply the egg escapement model. In this study, experiments were conducted at the Southwest Fisheries Science Center (SWFSC) and at CDFW to provide data to re-evaluate the laboratory protocols for drying female squid mantle tissues and to determine the relationship between fresh and preserved gonad weights. Results of these experiments demonstrated that slight modifications to the existing protocols significantly decreased laboratory processing time. Drying mantle tissue at 60°C, 64°C, 68°C, 72°C, or 76°C for 1, 2, 3, or 4 days achieved similar results as in drying the mantles for 14 days at 56°C. For female squid gonads, the regression model, Wp = 1.8980 x Wf - 0.5186, predicted the relationship between formalin preserved gonad weight (Wp) and fresh gonad weight (Wf) and explained 97% of the variability in the data. This model will allow new data (i.e. fresh gonad weights from 1.606 to 8.344 grams) to be combined with historical data (i.e., preserved gonad weights) and to be incorporated into the existing egg escapement model. Additionally, obtaining fresh gonad weights will save time and money since there is no longer a need to purchase or dispose of formalin, a hazardous chemical preservative. However, it should be noted that the prediction intervals for converted gonad weight is roughly 1.2 grams. Depending on the weight of the ovary, this uncertainty could impact the resulting egg escapement. As such, additional samples need to be collected to determine if the variability in converted gonad weight is acceptable or if the egg escapement model should be updated to allow for the accommodation of fresh, rather than formalin preserved, gonad weights.