Stock Identification of HaddockMelanogrammus aeglefinuson Georges Bank Based on Otolith Shape Analysis

Abstract

Otolith shape analysis was examined to determine its utility for stock identification of haddock Melanogrammus aeglefinus on Georges Bank. Otolith samples were collected from the Northeast Peak (eastern Georges Bank) and the Great South Channel (western Georges Bank) spawning components to examine stock continuity across Georges Bank. Otolith shape was described using 20 Fourier harmonics, four morphometric characteristics (area, length, width, and perimeter), and two shape indices (circularity and rectangularity). Potential confounding sources of variation (fish length, otolith position, age‐group, and year‐class) were examined and accounted for in the analyses before interpretation of spatial/stock differences. Significant age‐specific differences in otolith shape between eastern and western Georges Bank haddock indicated stock separation across the Bank. Classification success for each spawning component ranged from 63 to 80% across age‐groups and appeared to depend on growth rate differences. Otolith shape analysis has potential for stock identification of haddock on Georges Bank, but only for year‐classes with differing growth rates. The results of this study indicated an underlying stock structure within the Georges Bank transboundary haddock resource that may assist in defining consistent stock definitions used by the United States and Canada.

Southern flounder (Paralichthys lethostigma) stock structure inferred from otolith shape analysis

“…They conducted an exhaustive study of all 3 types of otolith pairs in which they found evidence of structuring among spawning groups of Atlantic cod (Gadus morhua) in the Northwest Atlantic, in addition to differences in otolith shape among age groups, sexes, and year classes. Begg and Brown (2000) used otolith shapes to challenge successfully the assumption of a single stock of haddock (Melanogrammus aeglefinus) at Georges Bank, and DeVries et al (2002) clarified previous tag and genetic data when they used otoliths to successfully distinguish stocks of king mackerel (Scomberomorus cavalla) from the Gulf of Mexico and the Atlantic that were sampled during their winter mixing off southern Florida. More recently, otolith shape analysis has been done at varying spatial scales for dolphinfish (Coryphaena hippurus [Duarte-Neto et al, 2008]), North Atlantic saury (Scomberesox saurus saurus [Agüera and Brophy, 2011]), and anglerfish (Lophius piscatorius [Cañas et al, 2012]) to help clarify questions about geographic population structure.…”

Otolith shape and size: The importance of age when determining indices for fish-stock separation

“…Otolith morphology varies markedly between species, however separate stocks of the same species, often identical physically, can sometimes be discriminated through subtle differences in otolith morphometrics. Expert otolith readers have drawn on otoliths to discriminate between: different ages or cohorts Burke et al 2009); sex (Cardinale et al 2004); diet (Gagliano and McCormick 2004) and of course stock (Begg and Brown 2000;Begg et al 2001;Brophy and Danilowicz 2002;Mérigot et al 2007;Duarte-Neto et al 2008). Some of these distinctions are more complex and more important to fisheries management (Begg et al 2005), which requires accurate measurements of stock composition/mixing, or stock movement, to inform decision making (Stransky 2005).…”

“…In some cases these measurements are supplemented with, or normalised by, measures such as fish length or weight (DeVries et al 2002;Stransky 2005;Mérigot et al 2007). Otolith boundaries are also extracted and represented, or encoded in different ways (transformed) prior to analysis with methods such as Fourier transforms (Begg and Brown 2000;Galley et al 2006;Bani et al 2013); and Elliptical Fourier transforms (Campana and Casselman 1993;Duarte-Neto et al 2008). Other methods of otolith boundary representation include Wavelets (Parisi-Baradad et al 2005), Curvature-Scale-Space (Begg et al 2005;Parisi-Baradad et al 2005) and the more recent Shapelet transform method (Lines et al 2012;Mapp et al 2013;Hills et al 2014).…”

Stock discrimination of two insular populations of Diplodus annularis (Actinopterygii: Perciformes: Sparidae) along the coast of Tunisia by analysis of otolith shape

“…The otolith shape is species specifi c (Sadighzadeh et al 2014). The outer shape of fi sh otoliths has been used in identifi cation of the species (Nielsen et al 2010) and/ or fi sh stock (Begg and Brown 2000, Cardinale et al 2004, Ponton 2006. The three-otolith pairs in teleost have a large morphological variability (Lombarte and Cruz 2007).…”