Egg, Larval, and Juvenile Surveys

Acoustic detection of larval fish aggregations in Galician waters (NW Spain)

“…The understanding of recruitment variability has been improved in recent decades through the concept of stock reproductive potential (Trippel 1999, Saborido-Rey & Trippel 2013 intimately linked to larval survivorship, through the parental effects on larval viability (Kamler 2005, Green 2008. Field applications of these results have been prevented by the inherent difficulty in getting proper data on larval distribution and abundance, to conduct correlation analysis (Lo et al 2009). Yet, recruitment in fish populations is largely determined during the early life-history stages by a combination of factors operating over multiple spatiotemporal scales, such as predation, starvation, and spatial mismatch with appropriate areas (Leggett &Deblois 1994, Subbey et al 2014, andreferences therein).…”

“…With the potential of the acoustic methodology, improved studies can be conducted to test with highest confidence the enduring theories and hypothesis on recruitment fluctuations (reviewed by Houde (2009) and Hare (2014)), and, in particular (i) to observe the density-dependent interactions between fish larvae and their predators and prey; (ii) to determine the drivers and factors affecting movement and distributional patterns of fish larvae; (iii) building and assessing quantitative drift models, pairing with the high-resolution ocean circulation models developed in past decades (Staaterman & Paris 2014); (iv) to understand the underlying processes determining the timing and duration of the recruitment interval, which is critical to assess the impact of specific mortality; (v) to study habitat selection and, consequently, a better estimation of recruitment at the stage of presettlement and, finally (vi) to estimate the spawning biomass using the larval production method, especially when fish eggs are not available or accessible, or they are difficult to identify (Lo et al 2009).…”

“…Additionally, understanding dispersal distance is important for a variety of reasons, including fisheries management, effective marine protected areas design, and control of invasive species (Cowen et al 2006, Becker et al 2007, Almany et al 2009, Cowen & Sponaugle 2009, Aiken & Navarrete 2011, Le Corre et al 2012. Long-time series of egg and larval abundance and distribution data facilitate a spatial comparison of spawning habitats (Van der Lingen & Huggett 2003, Ibaibarriaga et al 2007, Álvarez & Chifflet 2012 and play an important role in fishery management of many species through applying egg and larval production methods to estimate fish stock biomass (Motos et al 1996, Stratoudakis et al 2004, Lo et al 2009.…”

“…These conventional sampling methods, however, suffer from many well-known drawbacks, including those related with sampling devices, larval size and larval behavior, such as net avoidance, extrusion and clogging (Barkley 1972, Wiebe et al 1982, Leslie & Timmins 1989, Johnson & Morse 1994, Hernandez Jr et al 2011, and problems associated with the nature of sequential sampling. The high patchiness and low mean density, typically shown by larval distribution, contribute to increase in variance and uncertainty, and reduces precision of abundance estimations (Lo et al 2009). Methods that overcome such limitations are required (e.g., acoustic and molecular techniques).The virtues of echo sounder records are the speed of areal coverage and the real-time data presentation of the echogram.…”