Ecology of hake recruitment: implications for fisheries management
The European hake (Merluccius merluccius) is one of most important demersal species in North Atlantic marine ecosystems. Recently, the status of this species has deteriorated due to a sharp decline of spawning stock biomass (SSB) and recruitment because of overfishing. This has led the EU to implement recovery plans for both stocks (EC No. 811/2004 and EC No. 2116/2005).
The aim of this project is to analyze the ecological processes of hake recruitment, from egg production to the post-larva phase, when it changes from pelagic to demersal habits and recruits definitively to the population. Recruitment variability factors will be studied, mainly those related to spawning stock characteristics (length structure, variability of spawning time and area), but also the influence of environmental factors on early life stages growth and mortality. In parallel, new genetic methods based on telomere shortening and its relationship with age will be tested to solve hake ageing problems.
Finally, this project will improve knowledge about stock-recruitment relationship and will study its impact on current management mechanisms and recovery plans implemented by the EU will be assessed. To reach this goal, available tools will be used and improve through incorporation of new biological information. Eggs and larvae distribution patterns and abundance fluctuations will be studied and analyzed in relation to different hydro-climatic factors that may be acting at population level through recruitment. Results will be compared with hake reproductive biology parameters. This will allow us to describe ideal spawning scenarios and to describe spawning dynamic as well as relationship between spawning, hatchery and nursery areas, and how hake reproductive strategy guarantees spawning success and recruitment.
1.1. Developing new genetic techniques for age estimation and to determine population structure.
1.2. Estimating monthly egg production based on fecundity and spawning dynamics.
1.3. Dertermining egg quality and its relationship with maternal characteristics.
1.4. Compilation of a stock reproductive potential database.
2. Recruitment dynamic: larvae and juveniles
2.1. Defining larvae and juveniles (age 0) abundance and distribution during peaks of spawning activity.
2.2. Determining daily growth of larvae and juveniles during production peaks and its temporal variability.
2.3. Estimating alternative recruitment indices: Development and application of larval and juvenile indices.
3. Spawning and recruitment habitat
3.1. Characterizing environmental conditions in spawning and recruitment areas.
3.2. Compilation of an oceanographic parameters database about spawning and recruitment areas.
4. Relational ecologic analysis
4.1. Analysis of determining environmental factors in the larvae and juveniles abundance and distribution.
4.2. Analysis of stock reproductive potential influences on recruitment.
4.3. Analysis of historical oceanographic-climatic data series: Identification of mesoscale factors affecting on recruitment.
5. Management implications
5.1. Development and implementation of new stock-recruitment models.
5.2. Definig biological reference points considering recruits production based on new models.
5.3. Evaluating and suggesting strong management strategies to reduce uncertainity of stock-recruitment relationship.
- Institute of Marine Research (IIM- CSIC)
- Spanish Institute of Oceanography (IEO)
- Marine and Food Technological Center (AZTI-Tecnalia )
The first survey funded by the MINECO by mean of the project CRAMER: “Ecology of hake recruitment: implications for resource management” was CRAMER-0312, onboard the vessel Cornide de Saavedra, lasting 15 days, from 28 March to 13 February 2012. The survey was conducted on the Galician shelf (between Fisterrae and Cape Estaca de Bares), which was attended by 18 scientists from both the AZTI, the IEO and IIM.
During this first survey were collected more than 600 larvae of hake, determining that its distribution is limited within the water column mainly between 40 and 100 m, in the intermediate depthof the Galician shelf (90 to 200 m depth). For the first time weere obtained samples of pre-recruits, between 2 cm and 7 cm, which are established on the bottom surface, at least during daylight hours. These first results will allow a better focus and definition of areas and methodologies to a better understanding of the ecology of the species recruitment. During this first survey, were also captured a large number of juvenile hakes, which together with the larvae and pre-recruits obtained will allow further evaluation of condition and age studies of the species.
More details on the methodology and preliminary results, see Survey Report CRAMER-0312.
Second survey funded by the MINECO , by mean of the project CRAMER: “Ecology of hake recruitment: implications on resource management”, onboard the vessel Cornide de Saavedra, lasting 15 days, from 17 to July 31, 2012. The survey was conducted on the Galician shelf (between Fisterrae and Stake Bars), which was attended by 19 scientists from both the AZTI, as the IEO and IIM.
During this second survey were obtained 170 larvae of hake. Compared the results with the campaign in March, there was a general shortage of hake larvae in the area of study, establishing a concentration in front of A Coruña, making possible to hypothesize that the mechanism that concentrates larvae and retained them in this area may be related to the pattern of movement (meso-scale phenomena). The fishing net Baca captured the largest proportion of juveniles (4-25 cm) and was the sampler that captured the 5 smaller individuals of the entire campaign (4 cm). To conduct growth studies were collected a total of 416 pairs of otoliths (sagitta), of which 5 pairs correspond to pre-recruits, 255 juveniles (5 to 25 cm) and 156 adults.
More details on the methodology and preliminary results, see Survey Report CRAMER 0712.
To disseminate and communicate to society the importance of research in fishery resources in general and of the CRAMER project in particular, a blog was created as a complement to disseminate the scientific and professional work done by the team involved in the project, especially the work done during the oceanographic survey CRAMER0712: http://cramer0712.blogspot.com.es/
This project is funded by the Ministry of Science and Innovation (CTM2010-21856-C03-03).